Welding Heat Input Calculator
Calculate welding heat input (kJ/mm) and net heat input for SMAW, MIG, TIG, FCAW, and SAW processes.
Heat Input Formula HI = (V × I × 60) / (Travel Speed × 1000) — result in kJ/mm.
Where V = voltage (V), I = current (A), Travel Speed in mm/min.
Thermal Efficiency Factor (k) Not all heat enters the weld — some is lost to the arc and atmosphere. SMAW: k = 0.80 | GMAW/MIG: k = 0.80 | GTAW/TIG: k = 0.60 | FCAW: k = 0.80 | SAW: k = 1.00.
Net Heat Input HI_net = k × HI. Used in HAZ (heat-affected zone) calculations and preheat estimation.
Why Heat Input Matters High heat input: wider HAZ, slower cooling, reduced hardness — risk of softening in HSLA steels. Low heat input: faster cooling, higher hardness — risk of hydrogen-induced cracking in hardenable steels.