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Significant Figures Calculator

Significant Figures Calculator

Count the significant figures in any number, or round it to a chosen number of sig figs. Accepts decimals and scientific notation (e.g. 1.230e4), live as you type.

Count significant figures

Significant figures -

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Round to significant figures

Rounded result -

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The sig fig rules

Digits Significant? Example
Non-zero digits (1–9) Always 1234 → 4
Zeros between non-zero digits Always 105 → 3
Leading zeros Never 0.0052 → 2
Trailing zeros with a decimal point Yes 1.200 → 4
Trailing zeros without a decimal point Ambiguous 1200 → 2–4
Digits in scientific notation All of them 1.230e4 → 4

Frequently asked questions

What are significant figures?

Significant figures (sig figs) are the digits in a number that carry meaningful information about its precision. In a measurement, they are the digits you are confident about plus one estimated digit — 12.34 cm has four sig figs.

How do I count significant figures?

Count all non-zero digits, all zeros between non-zero digits, and all trailing zeros after a decimal point. Ignore leading zeros, and treat trailing zeros with no decimal point as ambiguous. For example, 0.004503 has 4 sig figs and 1.200 has 4.

How do I round to 3 significant figures?

Keep the first three digits starting from the first non-zero digit and round based on the fourth. π = 3.14159… rounds to 3.14, and 4,567 rounds to 4,570 (often written 4.57 × 10³ to make the precision clear).

Are trailing zeros significant?

It depends on the decimal point. In 1.200 the trailing zeros are significant (4 sig figs — the value was measured to the thousandths). In 1200 they are ambiguous: the number could have 2, 3, or 4 sig figs, which is why scientists write 1.2 × 10³ when they mean two.

How do sig figs work in scientific notation?

Every digit in the mantissa is significant; the exponent only moves the decimal point. 1.230 × 10⁴ has 4 significant figures and equals 12,300.