Significant Figures Calculator
Enter any number to instantly count its significant figures, view scientific notation, and see which digits are significant. Trailing zeros and leading zeros are handled automatically.
You can also round any number to a specific number of significant figures using the rounding tool below.
Round to N Significant Figures
How Significant Figures Work
Significant figures (sig figs) are the meaningful digits in a measured or reported number. They indicate the precision of a measurement and follow specific rules:
- All non-zero digits are always significant (e.g. 1234 has 4 sig figs).
- Zeros between non-zero digits are significant (e.g. 1002 has 4 sig figs).
- Leading zeros are never significant (e.g. 0.0045 has 2 sig figs).
- Trailing zeros after a decimal point are significant (e.g. 1.200 has 4 sig figs).
- Trailing zeros in a whole number are ambiguous without additional context such as a decimal point or scientific notation.
Frequently Asked Questions
What are significant figures?
Significant figures are the digits in a number that carry meaningful information about its precision. They include all non-zero digits, zeros between non-zero digits, and trailing zeros after a decimal point. Leading zeros are never significant because they only serve as placeholders.
Are trailing zeros significant?
It depends on context. Trailing zeros after a decimal point are always significant (e.g. 2.50 has 3 sig figs). However, trailing zeros in a whole number without a decimal point are ambiguous. For example, 1500 could have 2, 3, or 4 significant figures. Using scientific notation removes this ambiguity: 1.5 × 103 has 2, while 1.500 × 103 has 4.
How do you round to significant figures?
To round to N significant figures, start counting from the first non-zero digit. Once you reach the Nth significant digit, look at the next digit: if it is 5 or greater, round up; otherwise, round down. For example, 0.004562 rounded to 2 sig figs becomes 0.0046.
Why are significant figures important in science?
Significant figures reflect the precision of a measurement and prevent false precision when reporting results. In scientific calculations, the result should not have more significant figures than the least precise measurement used. This ensures that reported data honestly represents the accuracy of the instruments and methods used.