Weld Symbol Chart — Complete AWS Reference Guide

Anatomy of a Weld Symbol

Every weld symbol is built from the same components. Understanding each part is the foundation for reading any weld symbol on any drawing.

Arrow side means the side of the joint the arrow physically points to. Symbols placed below the reference line apply to the arrow side. Symbols placed above the reference line apply to the other side — the face opposite where the arrow lands.

When both sides need welding, you'll see symbols above and below the line — read each independently because leg sizes, lengths, and finishes can differ. The reference line itself never moves; only the placement of the weld symbol and dimensions changes which face of the joint is affected.

Groove Weld Symbols Chart

Groove angle appears inside the V, bevel, U, or J symbol — typically shown in degrees (e.g. 60° for a standard V-groove). This is the included angle of the groove prep, not the bevel angle on one plate face.

Root opening is the gap left at the bottom of the groove before welding. It's shown inside the symbol or noted as (R) with a dimension. Root opening allows the root pass to achieve full penetration; too little risks lack of fusion, too much requires more filler and can increase distortion.

Fillet Weld Symbol

The fillet weld symbol is a right triangle. The vertical leg of the triangle always faces left regardless of which side of the joint the weld is on. The number to the left of the symbol is the leg size. The number to the right is the weld length. If no length is specified the weld runs the full length of the joint.

For intermittent fillet welds the length and pitch are shown as two numbers separated by a dash — for example 3-8 means 3-inch welds spaced 8 inches apart center to center. The total number of welds can be specified in parentheses.

A fillet weld symbol both above and below the reference line means weld both sides. The sizes may differ on each side — read them independently. Always verify the specified leg size against AWS D1.1 minimum fillet weld sizes for the base metal thickness before welding. Use our Fillet Weld Strength Calculator to check load capacity against throat size.

Plug and Slot Weld Symbols

A plug weld is made through a hole in one piece of metal to fuse it to the piece beneath. The symbol is a rectangle on the reference line. The hole diameter is shown to the left, depth of fill to the right, and the angle of countersink inside the symbol if applicable. Plug welds are common in automotive and sheet metal work where lap joints need additional fastening points.

A slot weld is similar but the hole is elongated. The symbol is the same rectangle but the length and width of the slot are specified. Slot welds appear on structural drawings where a standard plug weld would not provide enough weld area for the required shear load.

Spot and Seam Weld Symbols

Spot welds are resistance welds — the symbol is a circle on the reference line. The diameter of the nugget is shown to the left, number of spots in parentheses, and pitch to the right. Spot weld symbols appear on sheet metal and automotive drawings and are also used for arc spot welds (Dardelet welds) on light gauge steel decking.

Seam welds are continuous resistance welds — the symbol is a circle with two horizontal lines through it. Length and pitch follow the same convention as fillet welds. Both spot and seam weld symbols may appear with a process designation in the tail to distinguish resistance welding from arc welding processes.

Supplementary Weld Symbols

Multiple supplementary symbols can appear on a single welding symbol. Read them in combination: a circle (all around) plus a flag (field weld) means weld the entire perimeter on site. A flush contour with G below it means grind the weld face flush after welding. Always apply every symbol on the reference line — missing one supplementary mark is a common inspection failure.

How to Read a Complete Weld Symbol — Example Walkthrough

Consider this welding symbol: a fillet weld with 3/8 to the left of the triangle, 4 to the right, the fillet symbol both above and below the reference line, a circle at the arrow junction, a flag on the reference line, and a flush contour with G below the weld symbol. Reading left to right: the arrow points to the joint. Below the line is a 3/8-inch leg fillet on the arrow side, 4 inches long. Above the line is the same — 3/8-inch leg, 4 inches on the other side. Both sides get fillet welds.

The circle means weld all around the joint perimeter — no gaps, continuous weld following the full outline. The flag means this weld is made in the field, not in the shop. The flush contour with G means grind each fillet face flush with the base metal after welding. The welder's job: travel to site, weld 3/8 fillets on both faces, 4 inches per segment, continuously around the joint, then grind flush. For interactive lookups by weld type, use our Weld Symbol Reference Tool. For joint geometry, see the Weld Joint Design Guide, Weld Joint Design Calculator, and Fillet Weld Strength Calculator. For when structural code compliance applies, read What Is AWS D1.1 and When Does It Apply?.