Math & Science Utility
Significant Figures Calculator
Count significant digits in a decimal representation and round a value to a selected number of significant figures.
Method
The rounding calculation uses decimal arithmetic rather than binary floating-point arithmetic and applies round-half-even handling for exact halfway cases. Leading zeros are not significant. Zeros between nonzero digits are significant. Trailing zeros after a decimal point are significant; trailing zeros in an integer written without a decimal point are treated as ambiguous placeholders and are not automatically counted as explicitly significant.
Worked example
Rounding 12345.678 to four significant figures gives 12350. Rounding the exact decimal 2.345 to three significant figures with half-even tie handling gives 2.34.
When this is useful
Useful for science and engineering coursework, laboratory reporting, measurement calculations, and checking the stated precision of decimal values.
Privacy
The values you enter into this calculator are processed in your browser by Practical Tools Hub application assets. The calculator does not need to send your calculation inputs to a third-party calculation service.
Limitations
Significant figures communicate reported precision; they do not create measurement accuracy. The meaning of trailing zeros can depend on notation and context. Scientific notation is usually clearer when a trailing-zero count would otherwise be ambiguous.