Heat Input
Calculating welding heat input
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Professional welding calculators
Free online tools for welding calculations. Calculate heat input according to EN ISO standards.
Free calculators, no sign-upISO-focused calculations
Steel Preheating
Preheating temperature according to EN 1011-2
Open calculatorSteel Weldability
Carbon equivalents and cracking parameters
Open calculatorIn the WeldStack app
Welder Qualification Range
Qualification range according to ISO 9606 (steels)
Learn moreIn the WeldStack app
Welding Cost
Cost of a weld: consumables, labour, energy and equipment
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Proving heat input against a WPS range
Enter current, voltage and travel speed and you get heat input in kJ/mm with the thermal efficiency factor k applied for the process. Arc energy is reported separately, because the two are routinely confused in welding procedure records and only one of them carries the efficiency factor.
Deciding whether a joint needs preheating — and how fast it will cool
The preheat calculator follows EN 1011-2 Method B: carbon equivalent CET from the steel composition, material thickness, diffusible hydrogen in the deposited metal and the heat input you intend to use. The result is a minimum preheat temperature computed from the standard, not a rule of thumb. The same page then returns the t8/5 cooling time to EN 1011-2 Annex D at that working temperature, so you can see whether the preheat you are about to specify puts the cooling rate where the steel needs it.
Assessing a steel you have not welded before
From a mill certificate composition you get CE (IIW), CET, Pcm and CEN side by side, so you can see which formula applies to the grade in front of you and how close it sits to the cold-cracking thresholds.
Planning a welder qualification test to ISO 9606
The qualification range calculator turns the test piece variables — process, product, filler material, thickness, diameter, position, weld details — into the certificate designation and the full range of qualification, for both EN ISO 9606-1:2017 and the consolidated ISO 9606 edition. It is part of the WeldStack application and requires a free account.
Working out what a weld actually costs
The welding cost calculator takes the joint geometry and your own rates and returns the cost per weld, per metre and per kilogram of deposited metal, split into filler metal, gas or flux, labour, energy and equipment. It also shows what a higher arc-on time factor is worth — usually far more than any consumable price. It is part of the WeldStack application and requires a free account.
Writing the WPS those numbers end up on
Heat input, preheat temperature and the material group all end up on a welding procedure specification. Our ISO 15609-1 guide lists what a WPS has to contain, clause by clause, and includes a free WPS template (XLSX) — no sign-up.
See what a WPS must containCommon questions
- Do I need an account to use these calculators?
- The heat input, preheating and weldability calculators run in your browser with no sign-up and no data sent anywhere. The welder qualification range calculator is part of the WeldStack application and needs a free account, like the registers it sits next to.
- Is heat input the same as arc energy?
- No, and confusing the two is a common audit finding. Arc energy comes from current, voltage and travel speed alone. Heat input multiplies that by the thermal efficiency factor k, which depends on the process — to EN 1011-1 that is 0.6 for TIG, 0.8 for MAG and MMA, and 1.0 for submerged arc. The heat input calculator shows both figures.
- Which standards do the results follow?
- Heat input and arc energy follow the conventions of EN 1011-1 and ISO/TR 18491. Preheat temperature follows EN 1011-2 Method B. The carbon equivalents are the standard CE (IIW), CET, Pcm and CEN expressions. The results are an engineering aid and do not replace a qualified welding procedure.
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Certificates expire while the welder keeps working
WeldStack reads welder certificates in any language, warns you before they expire, and keeps them with your WPS and WPQR documents in one system instead of folders and spreadsheets — free trial, no credit card.