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Free significant figures calculator (sig fig calculator): count significant digits, see which digits count, convert to scientific notation, and round to sig figs for chemistry, physics, and lab reports—without guessing trailing-zero rules.
Last updated: March 21, 2026
If you want to explicitly declare that the zeros at the end of a whole number are significant, just place a decimal at the end! Example: 1000. instead of 1000.
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Counting sig figs doesn't have to be confusing. Just remember these three categories for zeros.
Zeros at the very beginning of a number are never significant. They just exist to locate the decimal point.
Example: 0.0025 (2 sig figs)
Zeros trapped between two non-zero digits are always significant. They are measured numbers.
Example: 308 (3 sig figs)
Zeros at the end are significant only if the number contains a decimal point.
Example: 10.0 (3 sig figs)
vs 100 (1 sig fig)
Significant figures (sig figs) are the digits in a measured or calculated value that reflect real precision. They prevent you from reporting fake accuracy—like claiming a mass is 12.3456789 g when your balance only reads to the nearest 0.01 g. In chemistry, physics, and engineering, sig figs are how you communicate uncertainty honestly.
This tool highlights which digits count, shows a scientific notation form, and can round to a chosen number of sig figs—so you can match your instructor’s rules faster than doing it by hand on a deadline.
Let the mantissa digits (ignoring sign and the decimal dot) be d₁…dₙ. Let i be the index of the first non-zero digit, and j the index of the last non-zero digit. Let D indicate whether a decimal point is present.
If D = true: significant digits are all digits from position i through the end (includes meaningful zeros after the last non-zero).If D = false: significant digits are from i through j only (trailing zeros in a whole number are not significant).Exponent part (e.g. e-3 in 6.02e23) is not counted as a sig-fig digit in the highlight view.Count = number of highlighted mantissa digits.Rounding uses numeric conversion and exponential formatting to preserve the requested total digit count when you set “Round to Sig Figs.”
12.50 mL
Four sig figs: the trailing zero after the decimal is meaningful precision.
0.005020 M
Four sig figs: leading zeros are not significant; captive and trailing zeros can be.
1200 (no decimal)
Often two sig figs unless written as 1200. or in scientific notation—this is exactly why notation matters.
Same digit pattern, different meaning—compare sig fig counts for common student mistakes.
| Value | Sig figs | Quick rule |
|---|---|---|
| 0.00450 | 3 | Decimal present; trailing 0 counts |
| 4500 | 2 | No decimal; trailing zeros often not sig |
| 4500. | 4 | Decimal clarifies trailing zeros |
| 5.02×10³ | 3 | Digits in mantissa are sig figs |
Keep extra digits in intermediate steps, then apply sig fig rules once on the final answer (unless your teacher specifies otherwise). Pair this page with our Average Calculator and Standard Deviation Calculator for full lab workflows.
More math tools: Ratio Calculator · Molecular Weight · Factor Calculator.
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