Significant Figures Calculator
Type a number exactly as written (for example 0.004520 or 1500.) to count its significant figures, and optionally round it.
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The rules for significant figures
- All non-zero digits count: 123 has 3.
- Zeros between non-zero digits count: 1005 has 4.
- Leading zeros never count: 0.0045 has 2.
- Trailing zeros after a decimal point count: 4.500 has 4, and 0.004520 has 4.
- Trailing zeros in a whole number without a decimal point are ambiguous: 1500 could have 2, 3 or 4. Write 1500. or 1.500 × 10³ to make it clear.
Why they matter
Significant figures show how precise a measurement is. In physics and chemistry, an answer should not be more precise than the least precise value used: multiplying 2.5 (2 s.f.) by 3.14159 gives 7.9, not 7.853975. Type the number exactly as it is written, because the trailing zeros you type are part of the count.
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Works on mobileSame tool on your phone, tablet or desktop.
How it works
- Enter — type or paste your values or text.
- Get the result — it is worked out in your browser.
- Adjust — change the inputs to compare, or copy the result.
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