Fillet Weld Weight & Consumable Consumption Guide
In structural steel fabrication and pressure vessel manufacturing, “guessing” the amount of weld metal needed is a recipe for project delays and budget overruns. Whether you are preparing a bid for a massive infrastructure project or writing a Welding Procedure Specification (WPS), precision is non-negotiable.
Our Fillet Weld Weight Calculator is designed to provide engineers, NDT inspectors, and estimators with mathematically sound data to determine exactly how much filler metal is required for any given seam.
Fillet Weld Estimator
Accounts for deposition efficiency and reinforcement.
📐 The Geometry of a Fillet Weld
To calculate weld weight, we must first understand the cross-sectional area of the weld bead. A standard, equal-leg fillet weld forms a right-angle triangle.
Key Terminology:
- Leg Length (L or also called Z): The distance from the root of the joint to the toe of the fillet weld.
- Theoretical Throat (a): The distance from the root to the hypotenuse of the largest right-triangle that can be inscribed within the weld cross-section.
- Formula: a = L x 0.707
- Convexity/Reinforcement: The additional weld metal that extends beyond the theoretical face. In professional estimation, we typically add 15% to 20% to account for this.
🧪 The Math: How to Calculate Weld Weight
The weight of the deposited weld metal is a product of its volume and the density of the alloy.
1. The Area Formula
The area of the triangular cross-section is:
Area = L2/2
2. The Weight Formula
To find the total weight (W), we multiply the area by the length and the material density:
W = (L2/2) x Length x Density Reinforcement Factor
3. Calculating Consumption
To find the actual amount of consumables to purchase, you must divide the weight by the Deposition Efficiency (n):
Total Consumables = W/n
Pro Tip: Deposition efficiency varies by process. TIG (GTAW) is near 95%, while Stick (SMAW) is often only 60% due to stub-end loss and slag.
📊 Quick Reference: Consumption Table (Carbon Steel)
Based on 7.85 g/cm3 density and 20% reinforcement.
| Leg Size (mm) | Area (mm2) | Weight per Meter (kg/m) | Typical Process Efficiency |
| 3 mm | 4.5 | 0.042 | TIG: 95% |
| 5 mm | 12.5 | 0.117 | MIG: 92% |
| 6 mm | 18.0 | 0.170 | Flux-Core: 85% |
| 8 mm | 32.0 | 0.301 | Stick: 65% |
| 10 mm | 50.0 | 0.471 | Sub-Arc: 98% |
Deposition Efficiency: The ratio of deposited metal mass to the consumed welding consumables mass
| Solid wire | 95% |
|---|---|
| Flux−cored wire | 90% |
| Covered electrode | 55% |
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