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Calcimator

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
  1. Record the actual welding voltage (V) and amperage (A) from your power source during the pass.
  2. Measure travel speed in inches per minute (IPM) using a stopwatch over a marked length.
  3. Select the process efficiency: SMAW ~80%, MIG/FCAW ~85%, SAW ~100%, TIG ~60%.
  4. Read Heat Input (kJ/in) — compare against your WPS limits (typically 25–100 kJ/in for structural steel).
  5. Use Heat Input (kJ/mm) for metric WPS documents or international standards like ISO 15614.
  6. Check Approx Cooling Rate to assess risk of hard heat-affected zone microstructures in hardenable steels.

How the result changes with Travel Speed

Travel SpeedHeat Input
1121.82 kJ/in
366.67 kJ/in
653.69 kJ/in
902.67 kJ/in

What each input means

Voltage
Arc voltage measured during welding.
Amperage
Welding current (amps) during the process.
Travel Speed
Speed the torch or electrode moves along the joint.
Process Efficiency
Thermal efficiency factor: GMAW ~0.8, SMAW ~0.75, GTAW ~0.65, SAW ~0.95.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Voltage = 25, Amperage = 200, Travel Speed = 12, Process Efficiency = 0.8 = 4 input(s) provided
  2. Calculate Heat Input
    Heat Input
    20 = 20
  3. Calculate Heat Input
    Heat Input
    0.79 = 0.79
  4. Calculate Approx. Cooling Rate
    Approx. Cooling Rate
    25 = 25

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