1. Identify significant digits
Non-zero digits are significant, leading zeros are not, and zeros between significant digits are significant.
Precision and measurement calculator
Significant Figures Calculator
Count significant figures, round values to a chosen number of significant digits, convert numbers to scientific notation, and apply precision rules to arithmetic calculations.
Count significant digits
Round to precision
Arithmetic sig-fig rules
Rounded result
12.30
Sig. figures
4
Scientific form
1.230 × 10¹
Calculate significant figures and precision
Choose a mode to round a number, count significant figures, or calculate with sig-fig arithmetic rules.
Significant figures communicate measurement precision. This tool
follows common scientific conventions, but classroom instructions
may differ for exact numbers, counted quantities, trailing zeros,
logarithms, and intermediate rounding.
How the Significant Figures Calculator works
The calculator identifies meaningful digits, ignores non-significant leading zeros, preserves significant trailing zeros, and applies the correct precision rule for the selected operation.
2. Round at the correct position
The next digit determines whether the final retained digit stays the same or increases by one.
3. Apply operation-specific rules
Multiplication and division use significant figures; addition and subtraction use decimal-place precision.
Rounding Position
Place = 10^(floor(log10(|x|)) − significant figures + 1)
Multiplication and Division
Result uses the fewest significant figures among the inputs
Addition and Subtraction
Result uses the least precise decimal-place position among the inputs
Number type
Example
Significant-figure interpretation
Leading zeros
0.0045
Leading zeros only locate the decimal point, so this value has two significant figures.
Interior zeros
1002
Zeros between non-zero digits are significant, so this value has four significant figures.
Trailing decimal zeros
4.500
Trailing zeros after a decimal point indicate measured precision, giving four significant figures.
Whole-number trailing zeros
4500
Without a decimal point or scientific notation, trailing zeros are usually treated as ambiguous and not significant.
Frequently asked questions
Important rules for counting and calculating significant figures.
What are significant figures?
Significant figures are the meaningful digits in a measured or reported value, including digits that show its precision.
Are leading zeros significant?
No. Zeros before the first non-zero digit only position the decimal point and are not significant.
Are zeros between non-zero digits significant?
Yes. Interior or captive zeros are always significant.
Are trailing zeros significant?
Trailing zeros after a decimal point are significant. Whole-number trailing zeros without a decimal point are usually ambiguous.
How do sig figs work in multiplication and division?
Round the final result to the same number of significant figures as the input with the fewest significant figures.
How do sig figs work in addition and subtraction?
Round the result to the least precise place value among the input numbers rather than the fewest significant figures.
Why use scientific notation?
Scientific notation makes the intended significant figures clear, especially for very large or very small numbers and whole numbers ending in zeros.
Should intermediate calculations be rounded?
Usually keep extra digits during intermediate steps and round only the final result to avoid accumulated rounding error.