Enter the welding current, arc voltage, and travel speed (plus optional arc efficiency) into the calculator to determine the welding heat input.

Heat Input Calculator

By Travel Speed
By Time & Length
Max Heat Input Check

Heat Input Formula

The following formulas are commonly used to calculate welding heat input (energy per unit length). They are equivalent because travel speed v equals weld length L divided by time t.

HI=\eta\frac{VIt}{L}\\=\eta\frac{VI\cdot 60}{v}
  • Where HI is the heat input (energy per unit length, e.g., J/in or kJ/mm)
  • V is the arc voltage (V)
  • I is the welding current (A)
  • η is the arc efficiency (unitless, typically 0 to 1)
  • t is the welding time (s)
  • L is the weld length (in)
  • v is the travel speed (in/min); the factor 60 converts minutes to seconds so the result is in J/in

To calculate heat input using time and length, multiply current by voltage (to get power), multiply by time and arc efficiency, then divide by the weld length. To calculate using travel speed, divide by travel speed with the appropriate unit conversion (as shown above).

What is welding heat input?

Definition:

Welding heat input is the amount of energy delivered to the workpiece per unit length of weld. It depends on arc voltage, welding current, travel speed, and (optionally) arc efficiency.

How to calculate heat input?

Example problem:

The following example problem outlines the steps and information required to calculate a welding heat input.

First, determine the welding current. For this example, the welding current is 60 amps.

Next, determine the welding (arc) voltage. This example uses an arc voltage of 20 volts.

Next, determine the total time of welding. In this example, the time is measured to be 100 seconds.

Next, determine the length of the weld. For this example, the length of the weld is 10 inches.

Finally, calculate the welding heat input using the formula above (assuming η = 1):

HI = V * I * t / L

HI = 20 * 60 * 100/10

HI = 12,000 J/in