Complete Weld Symbol Chart — AWS A2.4 Welding Symbols Reference

AWS A2.4 defines the standardized system for specifying welds on engineering and fabrication drawings across North America. Every weld symbol conveys weld type, size, length, location, and finishing requirements in a compact notation understood by designers, detailers, fabricators, and inspectors. This reference covers the complete AWS A2.4 symbol system: the reference line and arrow convention, fillet and groove weld symbols with all dimension positions, plug and slot welds, supplementary symbols (field weld, weld-all-around, contour, finish), backing and spacer symbols, tail notation, and step-by-step reading procedures. Includes comparison with ISO 2553 (the international welding symbol standard), common interpretation mistakes, and a self-test section with answers.

1. The Welding Symbol — Basic Structure

Every AWS A2.4 welding symbol is built around a horizontal reference line. An arrow connects one end of the reference line to the joint on the drawing. An optional tail at the opposite end carries process, specification, or procedure notes.

                          TAIL (spec, process, or notes)
                           |
                           v
                    ┌──────────────────────────┐
  FINISH SYMBOL ──→ G                          │
  CONTOUR SYMBOL ─→ ─                          │ ← REFERENCE LINE
                    ───────────────────────────┤
                           ▲         ▲         │
                           │         │         │
              WELD SYMBOL  │   DIMENSIONS      │
              (arrow side) │   (size, length,  │
                           │    pitch, angle)  │
                           │                    │
                        ARROW ─────────────────→ JOINT

The fundamental rule: A weld symbol placed below the reference line indicates a weld on the arrow side of the joint (the side the arrow physically touches). A weld symbol placed above the reference line indicates a weld on the other side of the joint (the side opposite the arrow). Symbols on both sides mean the weld is made on both sides.

This convention is independent of drawing orientation. The arrow side is always the face of the joint that the arrow point contacts. On a T-joint, the arrow typically touches one face of the stem or the flange. On a butt joint, the arrow contacts the near-side groove face.

Dimensions — Position Convention

All dimensions have prescribed positions relative to the weld symbol:

2. Arrow Side vs. Other Side — Detailed Convention

The distinction between arrow side and other side is the single most important concept in reading weld symbols. Getting it wrong means the weld is placed on the wrong face of the joint.

Arrow side (symbol below reference line): The face of the joint that the arrow physically points to and touches. This is always the near side from the perspective of the drawing view. On a T-joint where the arrow touches the vertical stem, the arrow side is the stem face. On a lap joint, the arrow side is the top member at the lap.

Other side (symbol above reference line): The face opposite the arrow side. On a T-joint, if the arrow touches the stem, the other side is the opposite face of the stem. On a butt joint, this is the far-side groove face.

Both sides (symbol above AND below): Identical symbols above and below the reference line indicate the same weld type and size on both faces of the joint.

Example — T-joint with fillet on arrow side only:

     5/16
─────────────  ← Reference line
 \  (arrow)
  \
   → (touching stem)

The 5/16 in fillet weld goes on the face of the stem that the arrow touches. The opposite stem face receives no weld.

Example — T-joint with fillet on both sides:

     5/16
─────────────  ← Other side (above line)
     5/16
─────────────  ← Arrow side (below line)
     ↑
   ARROW

Both faces of the stem receive a 5/16 in fillet weld.

3. Fillet Weld Symbols — Complete Reference

The fillet weld symbol is a right triangle with the vertical leg nearest the reference line. The hypotenuse slopes away from the reference line. For a fillet weld on the arrow side, the triangle sits below the reference line. For the other side, it sits above.

Arrow-side fillet:              Other-side fillet:          Both sides:

     size                            size                        size
──────────────                  ──────────────              ──────────────
 \   │                          \   │                       \   │     \   │
  \  │                           \  │ (above line)           \  │     \  │ (above)
   \ │                            \ │                         \ │      \ │
    \│                             \│                          \│       \│
──────────────                  ──────────────              ──────────────
                                                              \   │
                                                               \  │ (below)
                                                                \ │
                                                                 \│
                                                             ──────────────

Fillet Weld Dimensions

Weld size (left of symbol): The leg dimension of the fillet, in inches (imperial) or millimeters (metric). This is the distance from the root to the toe along each leg, assuming equal-leg fillets. For unequal-leg fillets, both leg dimensions appear, separated by a plus sign: e.g., 3/8+1/4 indicates 3/8 in on one leg, 1/4 in on the other.

Weld length (right of symbol): For intermittent fillet welds, the length of each individual weld segment appears immediately to the right of the symbol. If omitted, the weld is continuous along the full joint length.

Pitch (after hyphen, right of symbol): The center-to-center spacing between intermittent weld segments. 2-6 means 2-inch-long welds at 6-inch center-to-center spacing.

Chain intermittent pattern: Identical intermittent welds directly opposite each other on both sides of the joint. The length and pitch are the same above and below the reference line, and segments are aligned.

Staggered intermittent pattern: Intermittent welds on opposite sides are offset by half the pitch. Notated by two sets of length-pitch dimensions, one for the arrow side and one for the other side, with the stagger dimension shown.

Fillet Weld Sizing Rules (AWS D1.1)

The minimum fillet weld size is governed by the thicker of the two parts being joined, per AWS D1.1 Table 5.7 (equivalent to AISC 360 Table J2.4):

The maximum fillet weld size at edges is: for material less than 1/4 in thick, the weld size may equal the material thickness; for material 1/4 in or thicker, the maximum fillet size is 1/16 in less than the material thickness, unless the drawing specifies the weld is to be built out to obtain full throat thickness.

4. Groove Weld Symbols — Complete Reference

Groove welds are deposited into a prepared groove between the faying surfaces of the base metal. The groove geometry (V, bevel, U, J, flare-V, flare-bevel, square) is machined, ground, or thermally cut before welding.

Groove Weld Symbol Shapes

Square:         V-groove:       Bevel:          U-groove:
──┤├──          ──\  /──        ──┤ /──         ──(  )──
                ── \/ ──        ── /──

J-groove:       Flare-V:        Flare-bevel:
──( /──         ──) (──         ──) /──

Groove Weld Dimensions

For groove welds, the root opening and groove angle appear inside the groove symbol:

  Groove angle → 60°   1/8 ← Root opening
                ────\  /────
                     \/

Complete Joint Penetration (CJP) vs. Partial Joint Penetration (PJP)

CJP groove welds: The weld metal extends through the full thickness of the joint. No size dimension appears — the CJP groove develops the full base metal strength. The absence of a size or depth callout communicates CJP.

PJP groove welds: The weld penetrates to a specified depth less than the full joint thickness. The depth of preparation appears in parentheses left of the symbol. For example, (5/8)V indicates a PJP V-groove with a 5/8 in depth of preparation.

PJP effective throat calculation (AWS D1.1):

• For groove angles >= 60 degrees: effective throat = depth of preparation
• For groove angles < 60 degrees but >= 45 degrees: effective throat = depth of preparation minus 1/8 in
• For groove angles < 45 degrees: effective throat = depth of preparation minus 1/4 in

5. Plug and Slot Weld Symbols

Plug weld: A circular hole in one member filled with weld metal to fuse it to an underlying member. The symbol is a circle (or rectangle for a slot) on the reference line.

Slot weld: An elongated hole in one member filled with weld metal. The symbol is an elongated shape.

Plug weld (arrow side):         Slot weld (arrow side):
     ↓ size
   ───○─── length               ───▭─── length
      │                              │
   ──────── reference           ──────── reference

Plug weld dimensions:

• Diameter (left of symbol): Hole diameter
• Depth of fill (inside symbol): Depth of weld metal fill
• Pitch (right of symbol): Center-to-center spacing for multiple plugs
• Angle of countersink (above or below symbol, if applicable)

Slot weld dimensions:

• Width (left of symbol): Slot width
• Length (right of symbol): Slot length (end-to-end)
• Depth of fill (inside symbol or per notes)
• Pitch: Center-to-center spacing for multiple slots

Plug and slot welds are common in lap joints where access is limited to one side, such as stiffener-to-web connections in built-up girders and overlapped plate splices.

6. Supplementary Weld Symbols

Supplementary symbols modify the basic weld symbol to convey additional requirements.

Field Weld Symbol

A filled triangular flag placed at the junction of the reference line and the arrow (pointing toward the tail) indicates the weld is to be made in the field (at the job site during erection), not in the fabrication shop.

                                ⚑ (flag)
────────────────────────────────────
     \  │
      \ │
       \│

Field welds typically require additional inspection, preheat, and weather protection. Shop welds (no flag) benefit from controlled conditions, positioning, and access.

Weld-All-Around Symbol

A solid circle at the junction of the reference line and the arrow indicates the weld is continuous around the entire perimeter of the joint. Used when all faces or edges of the connected part must be welded — for example, a plate welded to the face of a column on all four sides.

     ○ (circle at junction)
─────┴──────────────────────
     \  │
      \ │
       \│

Contour Symbols

A line above the weld symbol specifies the required weld face contour:

Finish Symbols

A letter above the contour symbol indicates the finishing method:

Example: Ground flush contour:

  G
  ─
────\  /────
     \/

V-groove with ground flush finish. G above the straight contour line.

7. Backing, Spacer, and Melt-Through Symbols

Backing Symbol

A rectangle placed on the side of the reference line opposite the groove symbol indicates a backing bar (steel, copper, or ceramic) is used at the root of the groove weld. The backing may be permanent (structural steel backing left in place) or temporary (removed after welding and back-gouging of the root pass).

  \  /   ← V-groove (arrow side)
───\/──── reference line
  ────    ← Backing rectangle (other side, behind the root)

Spacer Symbol

A rectangle placed on the same side as the groove symbol, straddling the reference line, indicates a non-consumable spacer at the root. Used to maintain root opening and alignment during welding.

Melt-Through Symbol

A filled semicircle on the side of the reference line opposite the groove symbol indicates that complete fusion through the material thickness is required, with root reinforcement visible from the opposite side. Unlike backing, no separate piece is used — the weld metal itself provides the root reinforcement.

8. Tail Information — Processes, Specifications, and Notes

The tail (at the right end of the reference line) carries supplementary information that cannot be encoded in the symbol geometry alone. When no supplementary information is required, the tail is omitted.

When no tail is shown: Default processes and procedures per the general notes or project specification apply.

9. AWS A2.4 vs. ISO 2553 — Key Differences

AWS A2.4 (American) and ISO 2553 (International/European) use different conventions. Engineers working on international projects must recognize both systems.

Practical consequence: A fillet weld drawn with ISO 2553 conventions showing a5 means a 5 mm throat thickness fillet (equivalent to approximately 7 mm leg). The same weld under AWS A2.4 would show 1/4 (leg dimension). Misreading the system can result in an undersized or oversized weld.

10. Reading Weld Symbols — Step-by-Step Method

Follow this systematic procedure to read any weld symbol on a drawing:

Step 1: Identify the Joint

Locate the arrow and identify which joint it points to. Determine which face the arrow touches — this is the arrow side. The opposite face is the other side. For branches, gussets, and stiffeners, trace the arrow carefully; incorrect identification of the arrow side is the most common field error.

Step 2: Read the Weld Type

Check what symbol shape appears on the reference line, both above and below:

• Right triangle = fillet weld
• V-shape = V-groove
• Single diagonal = bevel groove
• Curved shape = U or J groove
• Circle = plug weld
• Elongated rectangle = slot weld

Step 3: Determine Arrow Side vs. Other Side

If the symbol is below the reference line: arrow side weld. Above: other side weld. Both sides: weld on both faces.

Step 4: Read the Dimensions

Left of symbol = size. Right of symbol = length (and pitch if hyphen present). Inside groove symbol = root opening and angle. Parentheses = depth of preparation.

Step 5: Check Supplementary Symbols

Circle at junction = weld all around. Flag at junction = field weld. Contour line above = finish requirement. Letter above contour = finish method.

Step 6: Read the Tail

If a tail is present, read the specification, process, electrode class, or NDE requirement. If absent, default procedures apply per the project general notes.

11. Worked Examples — Reading Complete Weld Symbols

Example 1: Simple Continuous Fillet, Arrow Side

  1/4
──────
 \  │
  \ │
   \│

Reading: 1/4 in fillet weld on the arrow side, continuous for the full joint length. No tail — default process per general notes. No supplementary symbols.

Fabrication instruction: Deposit a continuous 1/4 in fillet along the entire joint on the face the arrow touches.

Example 2: Intermittent Fillet Both Sides, Weld-All-Around

       3/8   2-6
   ○ ────────────
       3/8   2-6
   ○ ────────────

Reading: 3/8 in fillet weld on both sides, intermittent: 2-inch-long weld segments at 6-inch center-to-center pitch, all around the joint perimeter.

Fabrication instruction: Weld 2-inch-long 3/8 in fillets every 6 inches around the entire perimeter on both faces.

Example 3: CJP V-Groove with Backing, Ground Flush

    G
    ─
────\  /─────
     \/
  ─────────   ← Backing rectangle

Reading: Complete joint penetration V-groove on the arrow side, ground flush finish (G), with a backing bar on the other side.

Fabrication instruction: Prepare a V-groove on the arrow side. Weld with backing on the far side. After welding, grind the weld face flush with the base metal surface.

Example 4: PJP Bevel Groove with Fillet Reinforcement

  (5/8)  /
─────── /──── (bevel groove, arrow side)
 \  │
  \ │
   \│ (fillet, other side)
   1/4

Reading: Partial joint penetration bevel groove on the arrow side, 5/8 in depth of preparation, plus a 1/4 in reinforcing fillet weld on the other side.

Fabrication instruction: Bevel the arrow side to 5/8 in depth, weld the bevel groove, then deposit a 1/4 in fillet on the other side for reinforcement.

Example 5: Field Weld, Both Sides Fillet, with Tail

       5/16           ⚑ SMAW, E7018
───────────────────────────────────
       5/16
───────────────────────────────────

Reading: 5/16 in fillet weld on both sides, field weld (flag), using SMAW process with E7018 electrodes. Continuous along the full joint length.

Fabrication instruction: This weld is to be made at the job site (not in the shop), using stick welding with E7018 electrodes. Deposit a continuous 5/16 in fillet on both faces of the joint.

Example 6: Staggered Intermittent Fillet

  1/4   2-8
─────────────  (other side)
  1/4   2-8
─────────────  (arrow side, offset 4 in)

Reading: 1/4 in fillet welds on both sides, intermittent — 2-inch-long segments at 8-inch pitch, staggered so that segments on opposite sides are offset by 4 inches (half the pitch).

Fabrication instruction: Weld 2-in segments of 1/4 in fillet every 8 inches on the arrow side. On the other side, weld matching segments offset by 4 inches from the arrow-side segments.

Example 7: Plug Weld

    5/8
────○──── 3-12

Reading: 5/8 in diameter plug weld on the arrow side, 3-inch pitch (center-to-center spacing between adjacent plugs), filling through the full thickness of the lapped member.

Fabrication instruction: Drill or punch 5/8 in diameter holes in the top member of the lap. Weld-fill each hole to fuse the top member to the bottom member. Center holes 3 inches apart.

Example 8: CJP with Weld-All-Around and Tail (Complex Production Symbol)

          ○                   GMAW, AWS D1.1
────\  /────────────────────────────────────
     \/

Reading: CJP V-groove on the arrow side, weld-all-around, using GMAW (MIG) process, per AWS D1.1. No root opening or angle shown — per prequalified joint detail. Continuous around the entire joint perimeter.

12. Common Mistakes in Reading Weld Symbols

Mistake 1: Confusing arrow side and other side. The most frequent field error. Always physically trace the arrow on the drawing to identify which face it touches. Do not assume the arrow side is the "top" or "front" — it is always the face the arrow point contacts.

Mistake 2: Assuming "no symbol above line = no weld on other side." Correct. An empty space above the reference line means no weld is specified on the other side. If the designer intended a weld there, they would place a symbol above the line.

Mistake 3: Misreading intermittent pitch as end-to-end spacing. 2-6 means 2-inch-long welds at 6-inch on-center spacing, leaving a 4-inch unwelded gap between segments. It does NOT mean 2-inch segments with 6 inches between the end of one and the start of the next (that would be 2-8).

Mistake 4: Ignoring the tail. When a tail specifies an electrode classification (e.g., E7018) or NDE requirement (e.g., UT 100%), these are mandatory, not advisory. Using an incorrect electrode or skipping specified NDE creates a non-conformance.

Mistake 5: Assuming CJP when dimensions appear in parentheses. A groove symbol with parenthetical dimensions, e.g., (5/8)V, is a PJP (partial joint penetration) weld, not CJP. CJP groove welds show no depth dimension — full penetration is implied by the absence of a size callout.

Mistake 6: Placing the field weld flag on the wrong end. The flag is always at the reference line-arrow junction, pointing toward the tail. A flag at the tail end is meaningless.

Mistake 7: Confusing the contour line with the reference line. The contour symbol (straight or curved line) sits above the weld symbol, not on the reference line. A straight line on the reference line is the reference line itself — not a flush contour callout.

Mistake 8: Using shop symbols for field welds on erection drawings. Erection drawings should use the field weld flag for all welds made on site. Shop drawings show shop welds (no flag). Confusing the two results in welds being made in the wrong location.

13. Self-Test — Weld Symbol Reading Quiz

Test your ability to read weld symbols. Answers follow the questions.

Question 1: A weld symbol shows 3/8 to the left of a right triangle below the reference line, with 4-12 to the right. A small circle sits at the arrow-reference junction. What does this specify?

Question 2: A V-groove symbol appears below the reference line with 60 and 1/8 inside the groove. No dimensions appear left of the symbol. What type of weld is this?

Question 3: Two right triangles appear — one above and one below the reference line — both with 5/16 to the left. A flag sits at the junction. What does the flag indicate?

Question 4: A bevel groove appears above the reference line with (1/2) to the left. Below the reference line sits a backing rectangle. Is this CJP or PJP, and on which side?

Question 5: A circle (not filled) sits on the reference line with 1/2 to the left and 4-12 to the right. What type of weld is this?

Answers:

A1: 3/8 in intermittent fillet weld on the arrow side, 4-inch-long segments at 12-inch center-to-center pitch, weld-all-around the joint perimeter.

A2: CJP V-groove on the arrow side with a 60-degree included groove angle and 1/8 in root opening. The absence of a size/depth dimension means complete joint penetration.

A3: 5/16 in fillet weld on both sides, field weld — to be made at the job site during erection, not in the shop.

A4: PJP bevel groove on the OTHER side (above reference line), 1/2 in depth of preparation, with a backing bar on the ARROW side (below reference line).

A5: 1/2 in diameter plug weld on the arrow side, 4 in length per slot or hole, at 12 in center-to-center pitch.

14. Frequently Asked Questions

What is the difference between a welding symbol and a weld symbol? A welding symbol is the complete notation including the reference line, arrow, weld symbol, dimensions, supplementary symbols, and tail. A weld symbol is just the geometric shape (triangle for fillet, V for V-groove, etc.) that sits on the reference line to indicate weld type. In practice, "weld symbol" is commonly used to mean "welding symbol," but on drawings the complete welding symbol conveys far more information than the basic weld shape alone.

How do I know whether a groove weld is CJP or PJP from the symbol alone? Absence of a depth dimension means CJP. If a depth of preparation appears in parentheses left of the groove symbol (e.g., (5/8)V), the weld is PJP. Additionally, the letter "E" (for effective throat) with a dimension explicitly indicates PJP. If neither depth nor an "E" callout is present, the weld is CJP by default.

What is the effective throat of a fillet weld and how is it calculated? The effective throat is the perpendicular distance from the root of the fillet to the face (hypotenuse). For equal-leg fillets, effective throat = 0.707 x leg size. A 1/4 in fillet has an effective throat of 0.177 in. The weld shear capacity is based on the effective throat area, not the leg size. For unequal-leg fillets, the effective throat is the shortest distance from the root to the face.

When should I use a field weld flag vs. a shop weld? Use the field weld flag for welds made at the project site during steel erection (column splices, beam-to-column connections, brace connections). Use shop welds (no flag) for welds made in the fabrication shop under controlled conditions. As a general rule: welded built-up sections and subassemblies are shop-welded; connections between shipping pieces are field-welded. Field welding is more expensive and requires more inspection, so minimize field welds in design where possible.

What is the minimum fillet weld size on a 3/4-inch plate? Per AWS D1.1 Table 5.7 / AISC 360 Table J2.4: for a material thickness of 3/4 inch (the thicker part joined), the minimum fillet weld size is 1/4 inch. This applies regardless of the load — it is a minimum size to prevent cracking from rapid cooling in thicker material, not a strength requirement.

15. Related Calculators and References

• Welded Connections Calculator -- fillet weld capacity and weld group analysis per AISC 360, AS 4100, EN 1993
• Weld Symbol Generator -- create AWS A2.4 and ISO 2553 compliant weld symbols
• Fillet Weld Size Chart -- minimum/maximum sizes and E70 capacity table
• Weld Electrode Reference -- E60XX, E70XX, E80XX electrode selection
• Steel Connection Types -- shear tab, end plate, moment connection overview
• Bolt Torque Chart -- bolt tightening reference
• Steel Fy and Fu Table -- structural steel strength properties
• Weld Design Checklist -- step-by-step weld design procedure

Disclaimer (Educational Use Only)

This page is provided for general technical information and educational use only. It does not constitute professional engineering advice, a design service, or a substitute for an independent review by a qualified structural engineer. Welding symbols must be interpreted per the governing code (AWS D1.1, AS 1554, EN 1090, or equivalent) and the project-specific welding procedure specification (WPS).

All real-world structural design depends on project-specific factors (loads, combinations, stability, detailing, fabrication, erection, tolerances, site conditions, and the governing standard and project specification). You are responsible for verifying inputs, validating results with an independent method, checking constructability and code compliance, and obtaining professional sign-off where required.

The site operator provides the content "as is" and "as available" without warranties of any kind. To the maximum extent permitted by law, the operator disclaims liability for any loss or damage arising from the use of, or reliance on, this page or any linked tools.