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Significant Figures Calculator

Count significant figures, round a value to a requested precision, or calculate with the correct addition, subtraction, multiplication, and division rules.

Count significant figures

ExampleSample values — edit any field to see your result.

Decimal or scientific notation, such as 1.200e3.

Results update as you type.

Significant figures

4

Estimated result

Significant digits
4, 5, 6, 0
Scientific notation
4.560 × 10⁻³
Last significant place
10^-6 place
Significant figures4

Count the significant digits written in a number, round to a selected number of significant figures, or perform arithmetic with the correct measurement- precision rule. Typed trailing zeros and scientific notation are preserved.

Formula

For multiplication and division, the result uses the smallest significant- figure count. For addition and subtraction, it uses the least precise decimal place.

12.34 × 5.6 = 69.104 → 69       (2 significant figures)
123.45 + 0.6789 = 124.1289 → 124.13 (hundredths)
Keep guard digits through intermediate work and round the final result once. Repeated intermediate rounding can compound error.

Examples

Count 0.004560

Leading zeros do not count; the trailing decimal zero does. The number has 4 significant figures: 4, 5, 6, and 0.

Round 0.004956 to three significant figures

The result is 0.00496, or 4.96 × 10⁻³.

Frequently asked questions

What digits count as significant figures?
All non-zero digits count, zeros between non-zero digits count, leading zeros do not count, and trailing zeros after a decimal point count. Trailing zeros in a whole number can be ambiguous unless notation makes the intended precision clear.
How do I round to significant figures?
Find the first non-zero digit, keep the requested number of digits, and inspect the next digit. If it is 5 or more, increase the last retained digit; otherwise leave it unchanged.
What is the rule for multiplication and division?
Round the final answer to the same number of significant figures as the operand with the fewest significant figures.
What is the rule for addition and subtraction?
Round the final answer to the least precise decimal place among the operands. This is a place-value rule rather than a significant-digit count.
Why is 1200 ambiguous?
Without a decimal point or scientific notation, it may mean two, three, or four significant figures. Write 1.2e3, 1.20e3, or 1.200e3 to state the precision explicitly.

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