Weld Symbol Chart
Complete welding symbols chart per ANSI/AWS A2.4 with every standard weld symbol and its meaning. Filter by category, search by name, and click any row for details. Covers groove welds, fillet welds, plug and slot welds, resistance welds, and supplementary symbols used on engineering drawings.
Elements of a Welding Symbol
A complete welding symbol consists of up to eight elements arranged around a reference line and arrow. The weld symbol (type ideograph) is placed below the reference line for arrow-side welds and above for other-side welds.
Fig. 1: Standard location of elements of a welding symbol per ANSI/AWS A2.4 — Machinery’s Handbook 29th Ed., p. 1476
Reading a Welding Symbol — Worked Example
This example shows a 3/8″ fillet weld callout on a T-joint. The left side is the welding symbol as it appears on a drawing; the right side shows the resulting weld.
How to read it:
- The arrow points to the T-joint where the weld is required.
- The fillet symbol (triangle) sits above the reference line, so the weld goes on the other side of the joint — opposite the side the arrow points to.
- 3/8 to the left of the symbol = 3/8″ leg size. A single number means both legs are equal (3/8″ × 3/8″).
- The cross-section on the right shows the result: a 3/8″ equal-leg fillet weld (highlighted in orange) at the T-joint.
| Symbol | Description | ||
|---|---|---|---|
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Back or Backing | Fillet & Other | Arc/crescent shape. Same symbol, two uses: a backing weld is applied first to support the root pass before the main groove weld, while a back weld is applied to the back side after the main weld. The tail of the welding symbol specifies which is required. Always placed on the opposite side of the reference line from the main weld symbol. |
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Bevel | Groove Welds | Vertical line with angled line. One member is beveled, the other left square. Arrow break indicates which member gets the bevel. |
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Concave | Contour & Finish | Downward-curving arc placed above/below the weld symbol. The finished weld surface must be dished inward (concave). Common for fillet welds where fatigue life is a concern. |
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Convex | Contour & Finish | Upward-curving arc placed above/below the weld symbol. The finished weld surface is permitted to crown above the base metal. This is the natural as-welded profile for many processes. |
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Edge | Fillet & Other | Two vertical lines with small flanges. Used for edge joints on thin sheet metal where one or both edges are flanged before welding. |
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Field Weld | Supplementary | Filled flag (pennant) at arrow/reference line junction, pointing toward the tail. Indicates the weld is to be performed at the erection site, not in the fabrication shop. |
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Fillet | Fillet & Other | Right triangle. The most common weld symbol. Used for T-joints, lap joints, and corner joints where two surfaces meet at approximately 90°. Size indicates leg length. |
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Flare-Bevel | Groove Welds | Vertical line with outward curve. Used where one rounded surface meets a flat surface (e.g., round bar to flat plate). |
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Flare-V | Groove Welds | Two outward-curving lines forming a flared V. Used where two rounded or curved surfaces meet (e.g., two round bars side by side). |
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Flush | Contour & Finish | Straight horizontal line placed above/below the weld symbol. The finished weld surface must be flush (flat) with the base metal. Often combined with a finish method letter (G, M, C). |
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J | Groove Welds | Vertical line with curved transition. One member has a J-shaped edge preparation, the other left square. Reduces weld volume on thick material. |
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Melt-Thru | Supplementary | Filled half-circle on opposite side of reference line from the weld symbol. Indicates 100% joint penetration plus visible reinforcement on the root side is required. |
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Plug or Slot | Fillet & Other | Rectangle. Weld made in a circular hole (plug) or elongated hole (slot) in one member to fuse it to the underlying member. Diameter, depth, spacing, and countersink angle can be specified. |
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Scarf | Groove Welds | Two parallel diagonal lines. Used for scarf joints in brazing only, not fusion welding. The angled mating surfaces increase bond area. |
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Seam | Resistance Welds | Circle with horizontal line through center. A continuous weld along the length of overlapping sheets, produced by rolling electrodes (RSEW). Length, pitch, and strength can be specified. |
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Spot or Projection | Resistance Welds | Circle. A localized weld joining overlapping sheets at a point. Resistance spot welding (RSW) uses electrode pressure and current. Projection welding uses raised dimples. Diameter or strength can be specified. |
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Square | Groove Welds | Two parallel vertical lines. Used for butt joints in thin material where no edge preparation (beveling) is needed. Root opening may be specified. |
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Stud | Fillet & Other | Circle with X inside. Indicates a stud (threaded fastener or shear connector) to be welded to the surface. Common in structural steel and sheet metal assemblies. |
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Surfacing | Fillet & Other | Wavy line. Weld metal deposited on an unjoined surface to build up thickness, provide wear resistance (hardfacing), or restore dimensions. Not a joint weld. |
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U | Groove Welds | U-shape with curved bottom. Both members have a J-shaped edge preparation. Used on thicker plate to reduce weld volume compared to a V. |
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V | Groove Welds | V-shape open at top. Both members are beveled symmetrically. Used for full-penetration butt joints on plate accessible from one or both sides. |
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Weld-All-Around | Supplementary | Circle at arrow/reference line junction. Indicates the weld extends completely around the perimeter of the joint. Used on pipe-to-plate, tube frames, and similar connections. |
Source: American Welding Society Welding Symbol Chart (AWS A2.4:1998); Machinery’s Handbook 29th Ed. pp. 1476–1484. Symbol images show arrow-side placement per the standard.
Dimension Placement Rules
Weld dimensions occupy specific positions around the basic weld symbol. The table below summarizes the placement convention defined in AWS A2.4.
| Position | Dimension | Example |
|---|---|---|
| S (E) — left of symbol | Depth of preparation; size or strength (E = effective throat) | 1/4, 3/8, 5/16 |
| R — within symbol area | Root opening; depth of filling for plug and slot welds | 1/16, 1/8 |
| A — within symbol area | Groove angle; included angle of countersink for plug welds | 60°, 45° |
| L–P — right of symbol | Length of weld and pitch (center-to-center spacing) | 3-6 (3″ long, 6″ centers) |
| F — above contour | Finish method (C = chipping, G = grinding, M = machining, R = rolling, H = hammering) | G = grinding |
| T — in tail | Specification, process, or other reference | GMAW, A5.18 |
| (N) — in parentheses | Number of spot or projection welds | (4) |
Dimension placement per ANSI/AWS A2.4 — Machinery’s Handbook 29th Ed., p. 1477
Common Welding Process Designations
When a specific welding process is required, its letter designation is placed in the tail of the welding symbol. These codes are standardized in ANSI/AWS A2.4.
| Code | Process | Common Name |
|---|---|---|
| SMAW | Shielded Metal Arc Welding | Stick welding |
| GMAW | Gas Metal Arc Welding | MIG welding |
| GTAW | Gas Tungsten Arc Welding | TIG welding |
| FCAW | Flux-Cored Arc Welding | Flux-core |
| SAW | Submerged Arc Welding | Sub-arc |
| PAW | Plasma Arc Welding | Plasma |
| RSW | Resistance Spot Welding | Spot weld |
| RSEW | Resistance Seam Welding | Seam weld |
| EBW | Electron Beam Welding | E-beam |
| LBW | Laser Beam Welding | Laser |
| SW | Stud Arc Welding | Stud weld |
| OAW | Oxyacetylene Welding | Gas welding / oxy-fuel |
Letter designations per ANSI/AWS A2.4-91 — Machinery’s Handbook 29th Ed., p. 1479
How to Use This Weld Symbol Chart
Use the category dropdown to filter by weld type (groove, fillet, resistance, supplementary, or contour/finish), or type a name in the search box to find a specific symbol. Click any row to highlight it and see the full description. Click a column header to sort.
When reading a weld callout on a drawing, start by identifying the basic weld symbol on the reference line, then read dimensions left-to-right. The size (leg or groove depth) is to the left of the symbol, and the length and pitch are to the right.
Frequently Asked Questions
What is the difference between a weld symbol and a welding symbol?
A weld symbol is the ideograph (small graphic shape) that indicates the type of weld, such as the triangle for a fillet weld or the V for a V-groove weld. A welding symbol is the complete instruction on a drawing, made up of eight possible elements: reference line, arrow, basic weld symbol, dimensions, supplementary symbols, finish symbols, tail, and specification or process reference. Per AWS A2.4, the weld symbol is one component of the larger welding symbol.
What does it mean when a weld symbol is above or below the reference line?
A weld symbol placed below the reference line means the weld is on the arrow side of the joint — the side the arrow points to. A weld symbol placed above the reference line means the weld is on the other side of the joint — opposite the arrow. If the symbol appears on both sides of the reference line, the weld is required on both sides. This arrow-side/other-side convention is defined in AWS A2.4 and is the most fundamental rule for reading welding symbols. Note: the symbol images in the table above show arrow-side placement only (below the reference line) to keep the table clean.
How do I read weld dimensions on a welding symbol?
Weld dimensions are placed around the basic weld symbol in specific positions: the weld size (leg size or groove depth) goes to the left of the symbol, the weld length goes to the right, and the pitch (center-to-center spacing for intermittent welds) follows the length separated by a dash. Root opening or depth of filling goes inside the weld symbol. Groove angle is placed outside the symbol. For example, “1/4 [fillet symbol] 3-6” means a 1/4-inch fillet weld, 3 inches long, on 6-inch centers.
What does the circle at the arrow junction mean on a welding symbol?
A circle at the junction of the arrow and reference line is the weld-all-around symbol. It means the weld extends completely around the joint, following the full perimeter of the connection. This is commonly used on pipe-to-plate connections, tube frames, and any joint where the weld must be continuous around the entire circumference.
What is the flag symbol on a welding symbol?
A filled flag (pennant) at the junction of the arrow and reference line is the field weld symbol. It indicates the weld is to be made in the field — at the job site — rather than in the shop during initial fabrication. This is common in structural steel erection where members are shop-fabricated but joined on-site. The flag points toward the tail of the welding symbol.
Related Calculators
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References
- Oberg, E. et al. Machinery’s Handbook, 29th Ed., Industrial Press, 2012 — Weld and Welding Symbols, pp. 1476–1484.
- ANSI/AWS A2.4:1998, Standard Symbols for Welding, Brazing, and Nondestructive Examination, American Welding Society.
Data last verified: April 2026
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