Welding Symbols Chart & Practice Lab

Q: What does a fillet weld symbol look like?

A fillet weld symbol is a right triangle. In AWS drawings, placement below the reference line means arrow side and placement above means other side.

Interactive Welding Symbol Explorer

Choose a weld type and side. The callout and joint view update together so you can connect the mark on the reference line with a simplified physical joint. These diagrams teach interpretation, not fabrication dimensions or weld design.

Weld symbol Placement Example size

Drawing callout

Simplified joint view

How to Read Welding Symbols Without Guessing

A complete welding symbol can contain a lot of information, but its backbone is simple: a reference line and an arrow. The arrow identifies the joint being called out. The horizontal reference line is where weld symbols, dimensions, supplementary marks, and other instructions are placed.

Weld symbol vs. welding symbol

A weld symbol is the individual graphical mark that identifies a weld type, such as a fillet or groove weld. The welding symbol is the full callout: arrow, reference line, weld symbol, dimensions, optional tail, and supplementary information.

Arrow side vs. other side

Below the reference lineArrow side

Above the reference lineOther side

Symbols on both sidesWelds specified on both sides

"Arrow side" does not mean the side of the drawing closest to you. It means the side of the joint to which the arrow points.

A nine-step decoding routine

Check the drawing standard and general notes. Confirm whether the drawing uses AWS A2.4, ISO 2553, or another documented convention.
Trace the arrow to the exact joint. Do this before decoding the shape.
Determine side significance. Arrow side, other side, or both.
Identify the basic weld symbol. Fillet, groove, plug/slot, spot, seam, edge, surfacing, or another type.
Read information to the left. Depending on weld type, this can include size or preparation-related dimensions.
Read information to the right. Depending on weld type, this can include length, spacing, or pitch.
Check supplementary symbols. Examples include all-around, field weld, backing, or melt-through.
Check contour and finish information. Do not treat finish letters as generic quality grades.
Read the tail and drawing notes. Look for process, WPS, code, inspection, or other referenced instructions.

This sequence is deliberately boring. Boring is good. A repeatable process is harder to screw up than "I recognize that shape, send it."

Guided decoder

Work through a sample callout one layer at a time.

Basic Welding Symbols Chart

The symbol shape tells you the weld type. Placement, dimensions, and supplementary marks tell you how the callout applies. Use the chart as a memory aid, then confirm the complete drawing context before production work.

Symbol family	What it communicates	Beginner watch-out
	Triangular weld geometry commonly used at T, lap, and corner joints.	The triangle's position above or below the line matters.
	Groove weld between square-cut edges.	Do not confuse the open parallel lines with an edge-weld symbol.
	Both mating edges are prepared to form a V-shaped groove.	Root opening and groove angle use their own positions.
	One member receives an angled edge preparation.	A broken arrow can identify which member is prepared.
	Curved preparation on both members forms a U-shaped groove.	Do not read the curved preparation like a straight bevel.
	One member receives a curved J-style preparation.	Member selection matters because the joint is asymmetric.
	Natural curvature of two rounded members forms the groove.	The geometry comes from member shape, not a standard V cut.
	A curved member meets a flat member to create the groove.	Do not interpret it as a conventional single bevel.
	Weld metal is deposited through a prepared opening in one member.	AWS A2.4:2020 changed how plug-weld diameter is shown.
	Specifies a discrete spot weld.	Size and strength information are not interchangeable.
	Specifies a seam weld, continuous or intermittent as detailed.	Read the entire callout before inferring process or side significance.
	Weld along edges of sheet or flanged members.	Do not confuse it with a square-groove mark.
	Deposits weld metal onto a surface for buildup or restoration.	This is surface deposition, not primarily a joint between two members.

Fillet welds: size, length, and pitch

A fillet weld symbol is a right triangle. Under AWS drafting conventions, the perpendicular leg of the fillet symbol is drawn on the left. A size shown to the left specifies fillet size. Values to the right can specify weld length and, for intermittent welds, pitch.

Groove symbols and dimensions

Groove symbols include square, V, bevel, U, J, flare-V, and flare-bevel configurations. Placement above or below the reference line still controls side significance. Groove callouts can communicate preparation depth, groove weld size/effective throat, root opening, and included angle. Their meaning depends on both placement and groove type.

Plug, slot, spot, and seam symbols

Plug and slot welds are made through prepared openings in one member to join it to another. AWS A2.4:2020 removed the diameter mark from inside the basic plug-weld symbol, while diameter remains part of plug-size dimensioning. For spot and seam welds, the 2020 edition also changed the role of dimensions to the left so that location is used for weld size rather than strength.

Dimensions: Left and Right Are Not Interchangeable

A useful beginner rule is that the location of a number is part of its meaning.

Fillet sizeCommonly shown to the left of the fillet symbol.

Weld lengthCommonly shown to the right.

Intermittent pitchShown with length to the right, as center-to-center spacing.

Groove detailsPreparation, root opening, throat/size, and angle use type-specific positions.

Different weld types use different dimension rules. Do not transfer a fillet rule blindly to a groove, plug, spot, or seam symbol.

Supplementary Symbols and Modifiers

Weld-all-around

An open circle at the junction of the arrow and reference line is the weld-all-around symbol. It tells the fabricator that the specified weld continues around the boundary of the indicated joint where the geometry supports that instruction.

Field weld

A flag at the arrow/reference-line junction identifies a field weld. It concerns where the weld is made, not torch travel direction.

Contour and finish

Contour symbols indicate the required face profile, such as flat/flush, convex, or concave. AWS A2.4:2020 clarified terminology and finishing practice: flat contour terminology is limited to fillet welds, while flush applies to groove, plug, and slot welds. When a finish-method letter is given, it identifies the required method rather than a generic quality score.

Melt-through and backing

Melt-through and backing symbols appear opposite the primary groove-weld symbol when applicable. Melt-through indicates required visible root reinforcement associated with penetration through the joint. Backing indicates material at the joint root used to support welding. They are not interchangeable.

What the Welding Symbol Does Not Tell You

A welding symbol is not a Welding Procedure Specification (WPS). It can tell you what the drawing requires at a joint, but it does not automatically provide the process variables needed to make the weld correctly.

Production work may also depend on:

the approved WPS;
project and drawing notes;
material and joint details;
governing code or contract requirements;
inspection or NDE requirements; and
qualified supervision or engineering direction.

If a symbol appears ambiguous or conflicts with another controlling document, get clarification. Do not invent a plausible interpretation and hope metallurgy is feeling charitable that day.

AWS vs. ISO welding-symbol systems

AWS A2.4 uses a single reference line. ISO 2553:2019 recognizes two systems: System A uses a dual reference-line convention, while System B uses a single reference line. ISO 2553:2019 is still the published international standard as of September 2026, although ISO has a replacement draft in development.

The practical lesson: confirm the governing standard before interpreting side significance. A familiar-looking symbol can be placed differently under another system.

For broader plan-reading practice, try the Blueprint Reading Practice Lab. If you are sorting out credentials, see our welding certification guide.

Interactive Welding Symbols Practice Lab

Pick a level and run a randomized 10-question session. You get an explanation immediately after each answer, plus a review summary of the topics you missed. This is self-assessment, not a qualification exam.

Choose a level and start when you are ready.

Common Welding Symbol Mistakes to Avoid

Reading the shape before tracing the arrow. You can identify the weld type correctly and still apply it to the wrong joint face.
Treating arrow side as near side. Arrow side is defined by the joint the arrow identifies, not where you are standing.
Ignoring above vs. below. Vertical placement on the reference line carries meaning in AWS drawings.
Reading a fillet size as weld length. Left and right placement are not decorative.
Treating pitch as the clear gap. Pitch is center-to-center spacing.
Reading the field flag as travel direction. It identifies field welding.
Treating the symbol as a complete WPS. Drawing geometry and welding procedure variables are different layers of instruction.
Applying AWS rules to ISO System A without checking. Confirm the drawing standard first.
Confusing quiz performance with physical qualification. Drawing literacy is one skill, not proof of welding competence.

Printable Welding Symbols Reference and Worksheet

Need something you can mark up at a desk or in class? These print views use the same verified rules as the page and avoid tiny screenshot charts.

TSNET Welding Symbols Quick Reference

AWS-oriented educational reference. Verify the governing drawing standard, WPS, and project documents before production work.

Below reference line
Arrow side

Above reference line
Other side

Left of fillet symbol
Fillet size

Right of fillet symbol
Length / pitch when specified

Circle at arrow junction
Weld-all-around

Flag at arrow junction
Field weld

Nine-step reading order

Check standard and notes.
Trace arrow to joint.
Determine side.
Identify weld symbol.
Read left-side dimensions.
Read right-side dimensions.
Check supplementary symbols.
Check contour and finish.
Read tail, WPS, code, and notes.

Remember: Intermittent pitch is center-to-center spacing, not clear gap.

Welding Symbols Practice Worksheet

A fillet symbol sits below the AWS reference line. Which side of the joint does it apply to?
A fillet symbol sits above the reference line. Which side does it apply to?
Explain the difference between a weld symbol and a welding symbol.
An intermittent fillet is 2 inches long on 6-inch pitch. What is the clear gap?
What should you do before reading the symbol shape?
What does a circle at the arrow/reference-line junction mean?
What does the field-weld flag communicate?
Why is a welding symbol not a substitute for a WPS?
What drawing feature can help identify which member is prepared for an asymmetric bevel or J groove?
Why should you verify whether a drawing uses AWS A2.4 or ISO 2553 before interpreting side significance?

Answer notes

Arrow side.
Other side.
The weld symbol is the individual weld-type mark; the welding symbol is the complete callout.
4 inches.
Trace the arrow to the exact joint and confirm the governing standard/notes.
Weld-all-around.
The weld is made in the field rather than in the fabrication shop.
The WPS supplies procedure variables and controls not contained in the graphical callout.
A broken arrow can identify the member to be prepared.
AWS and ISO System A can use different side-designation conventions.

Welding Symbol Literacy and Training

Reading symbols is one part of becoming useful in a fabrication environment. The current BLS occupation for welders, cutters, solderers, and brazers lists a May 2025 national median annual wage of $53,750. BLS projects about 40,300 openings per year on average from 2025 to 2035, with 2.4% employment growth over that decade. Those figures describe the occupation broadly; they do not tell you what a particular process specialty, credential, union path, employer, or region will pay.

Questions to ask a welding school about print reading

Is welding-symbol interpretation taught as a structured part of the curriculum?
Do shop assignments require students to fabricate from drawings rather than only follow verbal instructions?
Are students taught to connect drawing callouts to WPS instructions and shop procedures?
Are joint fit-up, preparation, measurement, and tolerances practiced hands-on?
Which welding processes, codes, and qualification tests does the program prepare students to encounter?

A good program should teach both sides of the job: what the drawing says and how to execute the work safely with real equipment.

Ready to build the hands-on side?

Compare welding training programs and ask how much real shop time, blueprint reading, joint preparation, and instructor feedback are built into the curriculum.

Compare Welding Training Programs

Also useful: how to become a welder and our guide to welding apprenticeships.

Frequently Asked Questions About Welding Symbols

What is the difference between a weld symbol and a welding symbol?

A weld symbol is the individual graphical mark that identifies a weld type. A welding symbol is the complete callout, which can include the reference line, arrow, weld symbol, dimensions, supplementary symbols, and tail.

What does a fillet weld symbol look like?

It is a right triangle. In AWS drawings, placement below the reference line means arrow side; placement above means other side.

What does pitch mean on an intermittent weld?

Pitch is the center-to-center spacing between weld segments. It is not the clear unwelded distance.

What does the field weld symbol mean?

The flag at the arrow/reference-line junction indicates that the weld is to be made in the field rather than the fabrication shop.

Can the tail be omitted?

Yes. When no process, specification, procedure, or other reference needs to be placed in the tail, the tail can be omitted.

Are AWS and ISO welding symbols the same?

No. They share many concepts, but side-designation conventions can differ. ISO 2553:2019 includes both dual-reference-line System A and single-reference-line System B. Always verify the drawing standard before interpreting the callout.

Sources and Standards Checked

American Welding Society, AWS A2.4:2020, Standard Symbols for Welding, Brazing, and Nondestructive Examination.
American Welding Society, AWS A3.0M/A3.0:2025, Standard Welding Terms and Definitions.
American Welding Society, AWS D1.1/D1.1M:2025-AMD1, Structural Welding Code - Steel, used only for contextual structural-code references.
ISO 2553:2019, Welding and allied processes - Symbolic representation on drawings - Welded joints.
U.S. Bureau of Labor Statistics, May 2025 OEWS and 2025-35 Employment Projections for SOC 51-4121.

Technical standards can change. The edition identified on the actual drawing or project documents controls production work.