More than one carbon equivalent formula
The fetched OmniCalculator page explicitly notes that there is more than one carbon equivalent formula. This rebuild follows that structure and calculates four outputs: CE (AWS), CE (IIW), Pcm, and CE (JWES).
Formulas used in the Omni workflow
The page formatting compresses the fractions, so the expressions below are the formulas interpreted from the fetched source text:
CE (AWS) = C + Mn/6 + Si/24 + (Cr + Mo + V)/5 + (Cu + Ni)/15
CE (IIW) = C + Mn/6 + (Cr + Mo + V)/5 + (Cu + Ni)/15
Pcm = C + Si/30 + Mn/20 + (Cu + Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B
CE (JWES) = C + Si/24 + Mn/6 + Ni/40 + Cr/5 + Mo/4 + V/14
Interpreting weldability
Omni states that AWS sees CE above 0.4% as having cold-cracking potential in the heat-affected zone, while the IIW table rates weldability from excellent up to poor. The FAQs also note that preheating may be necessary between 0.4 and 0.6, and is generally compulsory above 0.6.