Carbon Equivalent Calculator

Carbon Equivalent Calculator works out a steel's weldability from its chemistry. Enter the composition in weight percent and read the IIW carbon equivalent (CE), the Ito-Bessyo Pcm, the guideline weldability band and an indicative preheat straight away. It works completely offline and nothing you enter ever leaves your phone.

HOW IT WORKS
The app applies the two standard carbon-equivalent formulas used in welding:

1. IIW carbon equivalent (adopted by AWS D1.1 and BS EN 1011-2):
CE = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15
Best for plain-carbon and carbon-manganese steels of medium and higher carbon.

2. Ito-Bessyo critical metal parameter (JWES):
Pcm = C + Si/30 + (Mn + Cu + Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B
Preferred for modern low-carbon, micro-alloyed and TMCP steels, where the IIW CE reads pessimistically.

The CE is mapped to guideline bands: below about 0.40 the steel is readily weldable; 0.40 to 0.60 needs care with heat input, hydrogen and often preheat; above about 0.60 is difficult, with a high risk of hydrogen cracking. Above the readily-weldable band, an indicative preheat is estimated with a Seferian-type relation that folds in the section thickness and the diffusible-hydrogen level. The reason it all matters: higher carbon equivalent means the heat-affected zone hardens faster on cooling into crack-prone martensite, and preheat slows that cooling and drives off hydrogen.

WHAT YOU CAN DO
- Enter a full composition (C, Si, Mn, Cr, Mo, V, Ni, Cu, B) in weight percent
- Load typical compositions for A36, A572-50 and A514 as a starting point
- Read CE (IIW) and Pcm side by side and see which suits your steel
- Set plate thickness and hydrogen level for an indicative preheat guide
- Open Details for a step-by-step breakdown of every term and a weldability-band table
- Learn why carbon equivalent, cooling rate and HAZ hardness drive cracking

BUILT FOR CLARITY
A calm violet, temper-inspired design puts the headline CE first, with Pcm, preheat and the weldability band right beside it. Light and dark themes, a tiny download, no clutter and no account required.

AN ESTIMATE, NOT A WELDING PROCEDURE
This is an educational screening tool, NOT a substitute for a welding engineer or a qualified welding procedure. Welding procedure qualification, preheat and post-weld heat treatment are code activities. The governing code (AWS D1.1, ASME IX or EN 1011), a qualified WPS and the steel's actual mill certificate always govern. The weldability bands and the preheat figure are guides, not limits. Formulas and bands are from the IIW / TWI and Ito & Bessyo (JWES); the preheat relation is of the Seferian type. Verify every value against your code and procedure before welding.

PRIVACY
The app collects no personal data and works fully offline. Ads are served by Google AdMob, which may use an advertising identifier as described in Google's policies.

Download Carbon Equivalent Calculator for a quick, sensible read on how weldable a steel is before you strike an arc.