Significant Figures Calculator

Every non-zero digit is significant. Zeros between non-zero digits (captive zeros) are significant. Leading zeros are never significant. Trailing zeros count only when there is a decimal point, so 100 has 1 significant figure while 100. and 100.0 have 3 and 4.

Trailing zeros are ambiguous without a decimal point, so by convention they are not counted in a plain integer like 100. Writing 100. (with a trailing decimal point) or 1.00 x 10^2 makes it explicit that all three digits are significant.

Only the coefficient (mantissa) carries significant figures; the power of ten does not. So 6.00 x 10^-3 has 3 significant figures and 9 x 10^8 has 1. This calculator reads the mantissa and ignores the exponent when counting.

We keep the first N significant digits and round the rest using round-half-up. For example 1234 rounded to 2 sig figs is 1200, and 3.14159 to 3 sig figs is 3.14. The formatted result keeps trailing zeros so 2 to 3 sig figs reads 2.00.

Trailing zeros matter for sig figs but are lost when a number is stored. Entering 0.004560 as text preserves the final zero so it counts as significant, whereas the bare value 0.00456 would not show it.

Yes. Everything runs entirely in your browser. Nothing you type is uploaded, logged, or stored.