Engineering tool

Carbon Equivalent (CEV) Calculator

Calculate the IIW carbon equivalent from a steel analysis and read off what it implies for weldability and preheat.

Carbon (C) (wt %)

Manganese (Mn) (wt %)

Chromium (Cr) (wt %)

Molybdenum (Mo) (wt %)

Vanadium (V) (wt %)

Nickel (Ni) (wt %)

Copper (Cu) (wt %)

Carbon equivalent CEV —

Weldability —

Enter carbon at minimum; the alloying elements are optional and count as zero when blank.

Formulas used

CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15

Practical notes

This is the IIW formula, the one most widely quoted in steel specifications. Other formulas exist and give different numbers — always say which one you used.
CEV is an indicator, not a verdict. Section thickness, hydrogen level and restraint matter as much as chemistry.

Frequently asked questions

What CEV counts as weldable without preheat?

Below roughly 0.40 is generally welded without preheat, 0.40 to 0.50 calls for care, and above 0.50 normally requires preheat and hydrogen control. Thickness shifts these boundaries.

Why do different sources give different carbon equivalents?

Because there are several formulas — IIW, Ito–Bessyo (Pcm) and others — weighting the alloying elements differently. They are not interchangeable, so quote the formula alongside the number.