Fillet weld size and weld metal weight
Deposited weld metal scales with the square of leg length, which is why an oversized fillet is the most expensive habit in machine frame design. Enter the joint and see what the metal actually costs you.
Deposition efficiency is not applied — this is deposited metal, not wire consumed. For consumable purchasing add roughly 10–20% for MIG/MAG and more for SMAW.
Deposited weld metal
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across all welds
- Effective throat
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- Cross-section area
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- Deposited volume
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- Effective weld length
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- AWS D1.1 minimum leg
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- vs. a 6 mm fillet
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How this is calculated
For an equal-leg fillet the effective throat is 0.707 × leg and the theoretical cross-sectional area is leg² / 2. Volume is area × effective length; weight uses a steel density of 7.85 g/cm³. The convexity allowance accounts for the crown a real weld carries above the theoretical triangle.
The minimum leg size follows the AWS D1.1 table keyed to the thicker part joined: 3 mm up to 6 mm plate, 5 mm over 6 to 12 mm, 6 mm over 12 to 20 mm, and 8 mm above 20 mm. The minimum exists to keep the cooling rate down and avoid a hard, crack-prone heat-affected zone — it is not a strength requirement, and it overrides a smaller leg calculated from load alone.
Sizing from load, the code minimum and distortion all interact. The reasoning is inweld symbols on machine frame drawingsand controlling distortion on large weldments.
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Free to quote, reference or link with attribution. The calculation method is stated above so it can be checked rather than taken on trust.