What does arrow side versus other side mean?

In AWS A2.4 the arrow points to the joint. A symbol drawn below the reference line means the weld is on the arrow side, the side the arrow touches. A symbol above the line means the other side. Symbols on both sides call for welds on both faces of the joint.

What do the size and length numbers mean?

The number to the left of the weld symbol is the size: the leg length of a fillet or the depth of a groove. The number to the right is the weld length. A hyphenated pair like 2-5 means a 2-unit weld every 5 units center to center, an intermittent weld.

What is the circle at the bend in the reference line?

A filled circle at the junction of the arrow and reference line is the weld-all-around symbol, meaning the weld continues completely around the joint. A flag at that point is the field-weld symbol, meaning the weld is made in the field, not the shop.

What are the contour and finish symbols?

A straight bar over the weld symbol means a flush face, a curve means convex or concave. A letter beside it (G grind, M machine, C chip, R roll) specifies how the face is finished. These supplementary symbols control the final weld profile.

Does this replace reading the AWS standard?

No. It is a learning and quick-decode aid covering the common cases. Real drawings can use tail notes, multiple reference lines, and process references that demand the full AWS A2.4 standard. Always defer to the controlling drawing and standard for production.

What is the Weld Symbol Decoder?

Interactive builder for AWS A2.4 welding symbols. Choose weld type, arrow-side and other-side placement, size, length, pitch, and supplementary symbols like backing, melt-through, flush, convex, and concave. Outputs a rendered symbol and a plain-English description of what the weld requires. Runs in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Weld Symbol Decoder — Gera Tools

Name: Weld Symbol Decoder
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

Get one useful tool a week

Like this tool? Enter your email and we'll send you one genuinely useful Gera tool a week — plus a link to come back to this one. No spam, one-click unsubscribe any time.

AWS A2.4 weld symbols pack joint type, size, length, spacing, finish, and field-or-shop instructions into a compact mark on a reference line. Misreading the side or the size leads to wrong welds and rejected parts. This interactive decoder lets you build a symbol from its parts and reads it back to you in plain English, so you can learn the notation or check a drawing.

The anatomy of a weld symbol

A weld symbol consists of a reference line (horizontal) with an arrow at one end pointing to the joint, and one or more weld symbols hung from the line. Everything about position, size, and finish is encoded by what sits where:

above the reference line  -> other side (far side of joint)
below the reference line  -> arrow side (near side of joint)
both above and below      -> both sides
number left of symbol     -> size (leg of fillet, or groove depth)
number right of symbol    -> weld length
hyphenated pair (2-5)     -> intermittent: 2 units long every 5 center-to-center
circle at the bend        -> weld all around
flag at the bend          -> field weld (not shop)
bar over the symbol       -> flush contour finish
curve over the symbol     -> convex or concave contour
letter beside contour     -> finishing method (G=grind, M=machine, C=chip, R=roll)

Common weld symbol shapes and what they mean

Symbol shape	Weld type
Triangle (isoceles)	Fillet weld
V shape	Single-V groove
Square gap	Square groove
Half-V	Single-bevel groove
Circle	Plug or slot weld
Arrow pointing to surfacing	Surfacing / overlay

Worked examples

Example 1 — Shop fillet, arrow side: A triangle below the reference line with 1/4 to its left and 3 to its right means: a 1/4 inch fillet weld, 3 inches long, on the arrow (near) side, made in the shop.

Example 2 — All-around field fillet, both sides: The same triangle appearing both above and below the reference line, with a circle at the arrow-bend and a flag, means: equal fillet welds on both sides of the joint, all the way around, made in the field — typically for a structural tube attachment that needs a continuous weather-tight seal applied on site.

Example 3 — Intermittent fillet: A fillet symbol below the reference line with 3/16 on the left and 2-6 on the right: a 3/16 inch fillet, 2 inches long, repeated every 6 inches center to center on the arrow side. This pattern is common on thin webs and gussets to control heat distortion.

Example 4 — Double-V groove with flush ground finish: The V symbol above and below the reference line, with 3/8 on the left and a flat bar plus G on the tail, calls for a 3/8 inch double-V groove weld on both sides, finished flush by grinding. This is typical for full-penetration structural butt joints where a smooth surface is required.

Common decoding mistakes

Confusing arrow-side and other-side: the arrow does not point to where the weld goes — it points to the joint, and position on the reference line determines the side.
Missing the all-around circle: it is a small open circle at the bend, easy to overlook on a small-scale print.
Treating size as the throat: for a fillet, the symbol size is the leg length, not the theoretical throat. Throat = 0.707 × leg.

Treat this decoder as a learning and quick-check aid. For production, always defer to the controlling drawing and the complete AWS A2.4 standard.