Welding Heat Input Calculator
Arc energy from voltage, current and travel speed. Optionally apply a thermal efficiency factor, if the method you work to uses one.
Welding parameters
Fields start empty. Enter your own values, or load the worked example to see how it works.
V
A
in/min
Enter your values (or load an example) to see results. Fix any highlighted inputs.
Arc energy vs. heat input
Arc energy is the electrical energy delivered per unit length of weld. Heat input, in some standards, is arc energy multiplied by a thermal efficiency factor (k) for the process, because not all arc energy goes into the workpiece. Other codes simply call arc energy "heat input". Check which definition your code or WPS uses.
Formula used
Arc energy (kJ/mm) = V × A × 60 ÷ (travel speed in mm/min × 1,000) Arc energy (kJ/in) = V × A × 60 ÷ (travel speed in in/min × 1,000) Heat input = arc energy × k (only when you apply k) 1 kJ/mm = 25.4 kJ/in
This uses average voltage and current. For pulsed or waveform-controlled processes, some codes require instantaneous energy or power instead. This calculator does not do that.
Worked examples
24 V, 200 A, 300 mm/min Arc energy = 24 × 200 × 60 ÷ (300 × 1,000) = 0.96 kJ/mm (24.4 kJ/in) 25 V, 250 A, 15 in/min Arc energy = 25 × 250 × 60 ÷ (15 × 1,000) = 25 kJ/in With k = 0.8 entered by the user: 25 × 0.8 = 20 kJ/in
FAQ
›What efficiency factor should I use?
Use the value given in the standard or WPS you work to. Some standards publish factors by process; others don't use one at all. This calculator doesn't pick one for you.
›Is my heat input within limits?
Heat input limits come from your WPS and applicable code. This calculator only does the math.
›How do I measure travel speed?
Measure weld length and time the arc, then divide length by time. Convert to in/min or mm/min.