Significant Figures Calculator
Choose whether to round a number to a specific number of significant figures, count how many significant figures a number already has, or convert it to scientific notation.
Last updated: September 22, 2026
Frequently asked questions
What counts as a significant figure?
All nonzero digits (1-9) always count. Zeros between two nonzero digits count (like the 0 in 105). Leading zeros (before the first nonzero digit, like in 0.0042) never count. Trailing zeros only count if the number has a decimal point (2.50 has 3 sig figs, but 250 alone is ambiguous and is treated as 2 sig figs unless written as 250. or 2.50×10²).
How many significant figures does 0.004520 have?
4 - the leading zeros (0.00) don't count, but the 4, 5, 2, and the trailing 0 all count, since there's a decimal point (which makes that trailing zero deliberate, not just a placeholder).
Why is 12,000 ambiguous for significant figures?
Without a decimal point, it's unclear whether the trailing zeros were measured precisely or are just placeholders for the number's magnitude - it could represent 2, 3, 4, or 5 sig figs depending on the actual precision of the measurement. Writing it in scientific notation (1.2 × 10⁴ for 2 sig figs, 1.200 × 10⁴ for 4) removes the ambiguity.
How do I round a large number like 82,391 to 3 significant figures?
Identify the first 3 significant digits (8, 2, 3) and round based on the next digit (9, which rounds up), giving 82,400 - the calculator handles this automatically based on the number's magnitude, not just its decimal places.
What's the difference between significant figures and decimal places?
Decimal places count digits after the decimal point regardless of magnitude. Significant figures count meaningful digits regardless of where the decimal point falls - 0.00123 has 3 significant figures but 5 decimal places, while 123,000 has as few as 3 significant figures (if the zeros are placeholders) despite having 0 decimal places.
How is this different from the scientific notation shown on the exponent calculator?
The exponent calculator's scientific notation is a secondary readout for a power calculation's result, shown at whatever precision the raw math produces. This calculator is a dedicated tool for the reverse and adjacent tasks: rounding any number to a specific number of significant figures, counting how many sig figs a number already has, or converting a number to scientific notation with an exact sig-fig count you choose.
Why do significant figures matter in science and engineering?
They communicate the precision of a measurement - reporting more digits than were actually measured overstates how precisely something is known, while reporting too few loses real information. Calculations built from measured values are conventionally rounded to match the least precise measurement's significant figures, so the result doesn't imply more precision than the inputs actually had.