Welding Calculator
Enter your weld geometry and welding parameters to get joint strength, heat input, filler metal consumption, deposition rate, and estimated weld time. Supports fillet and butt welds, five welding processes, and four base materials. All results update instantly as you type.
Formula
Worked example
A single transverse fillet weld with leg size 8 mm, length 150 mm, and allowable tensile stress 150 MPa: effective throat = 0.707 x 8 = 5.66 mm; P = 5.66 x 150 x 150 = 127,350 N = 127.4 kN. Heat input example: 24 V, 200 A, travel speed 200 mm/min gives HI = (24 x 200 x 60) / (200 x 1000) = 1.44 kJ/mm (gross).
What does this welding calculator cover?
This calculator has three modes. The joint strength mode computes the allowable load capacity of fillet welds (single transverse, double transverse, parallel) and butt welds (single and double-sided) using the classic weld stress formula P = 0.707 x s x stress x l, consistent with AWS D1.1 and Eurocode 3. The heat input mode calculates the energy delivered per unit length of weld from arc voltage, current, and travel speed, with a selectable thermal efficiency factor for different processes. The consumable mode estimates the volume and weight of weld metal needed, total filler metal to order (adjusted for deposition efficiency), deposition rate, and arc-on time, supporting fillet, single-V groove, and double-V groove joints across five welding processes.
Weld strength formulas explained
For a fillet weld, the effective throat is 0.707 times the leg size (s), which is the shortest distance through the weld cross-section. A single transverse fillet weld carrying tension uses P = throat x sigma x l, where sigma is the allowable tensile stress and l is the weld length. Double fillets double that capacity. Parallel fillet welds are loaded in shear along the weld axis, so the formula uses allowable shear stress (tau) instead, giving P = 2 x throat x tau x l. Butt welds are full-penetration joints where the throat equals the plate thickness; the strength is P = t x l x sigma for a single-sided weld, or P = (t1 + t2) x l x sigma for double-sided. These expressions give the allowable force in newtons; the calculator converts to kilonewtons for convenience. Always apply a code-specific capacity reduction factor before comparing with your design load.
Understanding heat input and why it matters
Heat input is the electrical energy delivered to the weld per unit length: HI = (V x I x 60) / (travel speed x 1000), in kJ/mm. The thermal efficiency factor k (0.60 for SMAW and GTAW, 0.80 for GMAW/FCAW, 0.90 for SAW) accounts for arc energy that does not enter the workpiece. AWS D1.1 uses a gross formula without this factor; the European standard EN 1011-1 includes it. Heat input controls the heat-affected zone (HAZ): too high and HAZ grains coarsen, reducing toughness; too low and rapid cooling can cause hydrogen cracking in hardenable steels. The chart in this calculator plots heat input across a range of travel speeds for your voltage and current, making it easy to see how a small change in speed shifts the result.
Estimating wire consumption and weld time
The cross-sectional area of deposited weld metal depends on joint geometry: a fillet weld of leg size s has area 0.5 s2, a single-V groove has area approximately 0.6 s2, and a double-V groove approximately 1.2 s2. Multiplying by weld length gives volume (cm3), and multiplying by the material density gives the deposited weight in kilograms. Because some electrode or wire is lost to spatter, fume, or stub ends, the actual consumable purchased must be divided by the deposition efficiency: 92-95% for GMAW, 83-85% for FCAW, 60-65% for SMAW, 97-98% for GTAW and SAW. The deposition rate (kg/h) comes from the wire feed speed and wire cross-section area for wire-feed processes, giving you an arc-on time estimate as well.
Deposition efficiency and typical heat input by welding process
| Process | Deposition efficiency | Typical heat input (kJ/mm) | Notes |
|---|---|---|---|
| SMAW (Stick) | 60-65% | 1.0-2.5 | Stub-end losses; high spatter |
| GMAW (MIG/MAG) | 90-95% | 0.3-1.5 | Spray, globular, or short-circuit transfer |
| FCAW (Flux-Core) | 80-85% | 0.8-2.0 | Gas- or self-shielded; some slag loss |
| GTAW (TIG) | 95-98% | 0.2-0.8 | Near-zero spatter; slowest process |
| SAW (Submerged Arc) | 96-99% | 2.0-5.0 | High current, deep penetration |
Deposition efficiency figures from AWS Welding Handbook vol. 1. Heat input ranges are typical; always refer to your WPS.
Frequently asked questions
What is the effective throat of a fillet weld?
The effective throat is the shortest distance from the root of the weld to the face, measured through the weld metal. For a standard equal-leg fillet weld it is 0.707 times the leg size (s). This dimension controls the stress in the weld throat and is the critical value in all fillet weld strength calculations. Deep-penetration GMAW processes can increase the effective throat slightly, but this is only credited when specifically qualified.
How is heat input calculated in welding?
Heat input (kJ/mm) = (arc voltage x welding current x 60) divided by (travel speed in mm/min x 1000). This gives the gross heat input. The net heat input adds a thermal efficiency factor k, which accounts for the fraction of arc energy actually absorbed by the workpiece: about 0.60 for SMAW and GTAW, 0.80 for GMAW and FCAW, and 0.90 for SAW. AWS D1.1 uses the gross formula; EN 1011-1 uses the net formula.
What is deposition efficiency and why does it matter?
Deposition efficiency is the percentage of the electrode or wire that ends up as weld metal in the joint. The rest is lost to spatter, fume, stub ends (for SMAW rod), and slag. GMAW has the highest efficiency (90-95%) because it uses a continuous wire with no stub ends and relatively low spatter. SMAW is lowest (60-65%) because of stub-end waste and higher spatter. Knowing the efficiency lets you order the right amount of consumable - buying only what is deposited would leave you short.
Which welding process produces the highest heat input?
Submerged arc welding (SAW) typically produces the highest heat input, often 2-5 kJ/mm, because it uses high currents (up to 1000 A or more) and relatively slow travel speeds. This can be beneficial for thick plates requiring deep penetration but must be carefully controlled for materials sensitive to HAZ toughness loss, such as quenched-and-tempered steels. GTAW produces the lowest heat input, often below 0.5 kJ/mm, making it suited for thin materials and heat-sensitive alloys.
Can I use this calculator for structural design?
This calculator uses standard weld strength formulas from AWS D1.1 and classical machine-design references, making it a reliable first estimate and a check against hand calculations. For final structural design, always refer to the applicable code (AWS D1.1, AISC 360, EN 1993-1-8, AS 4100, etc.), apply the required capacity reduction factors, and have the design reviewed by a qualified structural engineer. Code requirements for weld size, minimum throat, and inspection criteria must also be verified.
What is the difference between a transverse and a parallel fillet weld?
A transverse fillet weld runs perpendicular to the applied load direction. The load is resisted primarily as tension through the throat, and these welds are the strongest in terms of force per mm of weld. A parallel fillet weld runs parallel to the load direction and is loaded in shear along the weld axis. Parallel fillets are typically 20-25% weaker per unit length than transverse fillets of the same size, which is why the shear stress (tau) rather than tensile stress (sigma) governs the formula.