Carbon Equivalent Calculator
Calculate the carbon equivalent of a steel from its chemical composition using the three standard formulas — CEV (IIW), Pcm (Ito-Bessyo) and CET (EN 1011-2) — and get an immediate read on weldability and preheat requirements.
Composition (weight %)
Guidance is indicative. Preheat also depends on thickness, joint restraint, hydrogen level and heat input — follow EN 1011-2 or AWS D1.1 for the actual procedure.
The formulas
- CEV (IIW): C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15
- Pcm (Ito-Bessyo): C + Si/30 + (Mn+Cu+Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B
- CET (EN 1011-2): C + (Mn+Mo)/10 + (Cr+Cu)/20 + Ni/40
Weldability guide (CEV, IIW)
| CEV | Weldability | Typical action |
|---|---|---|
| < 0.40 | Readily weldable | No preheat normally required |
| 0.40 – 0.45 | Weldable with care | Low-hydrogen consumables; consider preheat on thick section |
| 0.45 – 0.50 | Preheat usually required | Preheat, low-hydrogen process, control interpass temperature |
| > 0.50 | Difficult | Preheat + controlled heat input; consider PWHT |
Frequently asked questions
What is carbon equivalent (CE)?
Carbon equivalent expresses the combined effect of carbon and alloying elements on hardenability and weldability as a single number. The higher the CE, the greater the risk of hard, crack-prone microstructure in the heat affected zone.
What CE value is considered weldable?
As a general guide for the IIW formula: below 0.40 is readily weldable, 0.40-0.45 needs care, 0.45-0.50 usually requires preheat, and above 0.50 requires preheat plus controlled heat input and possibly post-weld heat treatment.
What is the difference between CEV and Pcm?
CEV (IIW) suits carbon and carbon-manganese steels with carbon above about 0.18%. Pcm (Ito-Bessyo) was developed for modern low-carbon microalloyed steels where CEV overestimates the risk. CET (EN 1011-2) is used for preheat calculation in European practice.
Where do I get the chemical composition?
From the mill test certificate for your specific heat, or from the grade datasheet for typical ranges. Our steel grade pages list nominal composition ranges for hundreds of grades.
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