Significant Figures Rounder

About this calculator

Significant figures (sig figs) are the digits in a number that carry real measurement precision — all non-zero digits, zeros between non-zero digits, and trailing zeros after a decimal point count, while leading zeros (like the 0 in 0.0042) do not. Rounding to a set number of sig figs, rather than to a fixed number of decimal places, keeps a result honest about how precisely it was actually measured.

Scientists and engineers round to significant figures so that a calculated answer never implies more precision than the original measurements support — multiplying a length measured to 2 sig figs by one measured to 4 sig figs should give an answer reported to 2 sig figs, not 4. It shows up constantly in chemistry lab reports, physics problem sets, and engineering specs, where reporting 3.14159265 when your instrument only reads to three digits would be misleading.

This calculator rounds any number to the exact count of significant figures you specify, handling the zero-counting rules automatically.