Welding / procedure check

Weld Heat Input Calculator

Calculate arc energy and efficiency-adjusted heat input from voltage, current, travel speed, and process efficiency.

01 / Engineering inputs

Live calculation

Arc voltage

Use the applicable average value for the qualified procedure.

Welding current

Use the applicable average value for the weld pass.

Travel speed

Weld length divided by arc travel time.

Process efficiency preset

Preset values follow the cited TWI comparison; use the governing code or procedure.

Thermal efficiency

Heat input = arc energy × efficiency.

Formula, scope & sources

How this calculator works

Arc energy

AE = (V × I × 60) / (travel speed × 1000)

The result is kJ/mm when travel speed is mm/min, or kJ/in when travel speed is in/min.

Net heat input

HI = efficiency × AE

Some American codes use “heat input” for the unadjusted arc-energy value. This calculator reports both values explicitly.

Production application disclaimerCompare the result with the applicable WPS/PQR and governing code. Average voltage multiplied by average current may not represent true power for waveform-controlled processes; use measured energy or power when the procedure or code requires it.

Reference basis: Lincoln Electric explanation of ASME Section IX calculations · TWI: arc energy versus heat input

Implementation: Original MfgWorkbench calculation code, independently verified against cited formulas and worked examples. Last reviewed September 4, 2026.

Worked example: convert a timed weld into heat input

This arithmetic example uses 24 V, 180 A and 250 mm/min travel speed. If a measured 125 mm run takes 30 seconds of arc travel, speed is 125/(30/60) = 250 mm/min. Use a consistently defined run length and arc-travel time; do not include unrelated handling time.

Quantity	Calculation	Result
Electrical power	24 × 180 / 1000	4.32 kW
Arc energy	24 × 180 × 60 / (250 × 1000)	1.0368 kJ/mm
Heat input at assumed η = 0.80	1.0368 × 0.80	0.82944 kJ/mm
Same heat input per inch	0.82944 × 25.4	21.067776 kJ/in

The same travel speed is 9.84252 in/min. Entering that numerical value while leaving the calculator in metric mode would describe a much slower weld and give a much larger energy per unit length.

Choose the result your procedure actually requires

The efficiency-adjusted value is not automatically the quantity a code calls heat input. Record voltage/current measurement method, travel speed, the applied efficiency and the definition required by the governing procedure. These invented inputs demonstrate units; they are not a WPS or recommended welding settings. Pulsed or waveform-controlled processes may require measured energy rather than the product of separate average readings.