Heat Input Calculator
Calculate welding heat input in kJ/in and kJ/mm along with estimated cooling rate and HAZ width.
Inputs
V
A
in/min
Results
Heat Input
20 kJ/in
Heat Input0.79 kJ/mm
Approx. Cooling Rate25 °F/s
Estimated HAZ Width1.2 mm
How to Use This Calculator
- Record the actual welding voltage (V) and amperage (A) from your power source during the pass.
- Measure travel speed in inches per minute (IPM) using a stopwatch over a marked length.
- Select the process efficiency: SMAW ~80%, MIG/FCAW ~85%, SAW ~100%, TIG ~60%.
- Read Heat Input (kJ/in) — compare against your WPS limits (typically 25–100 kJ/in for structural steel).
- Use Heat Input (kJ/mm) for metric WPS documents or international standards like ISO 15614.
- Check Approx Cooling Rate to assess risk of hard heat-affected zone microstructures in hardenable steels.
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