Common logarithm—inverse of powers of 10 (educational).
The page computes y = log₁₀(x) using Math.log10 when available, otherwise ln(x) ÷ ln(10). The argument must be a finite x > 0 (logarithm of zero or negatives is not modeled here).
This calculator uses plain decimal numbers. If a result looks wrong, check whether you used a comma instead of a dot (or vice versa) where the field expects one.