Free Calculator - No Login

Welding Heat Input Calculator.

Enter your voltage, amperage, and travel speed for instant heat input in kJ/in - required for AWS D1.1 and ASME Section IX procedure qualification records.

Heat Input Calculator
V
A
in/min
19.0
kJ / inch
Normal Range
Heat Input = (V × A × 60 ÷ Travel Speed ÷ 1000) × Process Efficiency
Get the App - Android Get the App - iOS
Understanding It

What the number means.

1

Heat input drives the cooling rate

Higher heat input means slower cooling, which generally lowers hardness and reduces cracking risk in many steels - but too much can hurt strength and toughness, and increase distortion.

2

Your WPS sets the real limits

This calculator gives you a working number, but the qualified Welding Procedure Specification (WPS) for your job is the actual authority on acceptable heat input range - always check it first.

3

Process efficiency isn't optional

The raw V×A×60/travel-speed number overstates actual heat input, because every process loses energy to spatter, radiation, and arc characteristics. That's what the efficiency factor corrects for.

4

Document it for your PQR

For code work, log voltage, amperage, travel speed, and the resulting heat input on your Procedure Qualification Record alongside the joint, material, and process details.

In the App

50+ tools.
One app.

The heat input calculator is one of over 50 charts, calculators, and tools in Pocket Welder Helper - pipe offset, weight, bend planner, table legs, cost estimator, and more, all working offline.

Color-coded rating: Low / Normal / High / Very High
Code limits for AWS D1.1, ASME IX, API 1104
PQR documentation guidance built in
Google Play App Store
FAQ

Common questions.

Heat input equals voltage times amperage times 60, divided by travel speed in inches per minute, then divided by 1000 to get kilojoules per inch. A thermal efficiency factor specific to the welding process is then applied for code calculations.
It depends heavily on material, thickness, and process, but many structural steel welds fall somewhere between 15 and 45 kilojoules per inch. Procedure qualification records and the applicable code always take priority over a general range.
Codes like AWS D1.1 and ASME Section IX require heat input to fall within the range established by a qualified welding procedure. Too much heat input can reduce strength and increase distortion; too little can cause poor fusion or excessive hardness in certain steels.