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Enter one number
Use standard notation, a decimal, or scientific notation such as 1.20e3.
Free Sig Fig Calculator
A sig fig calculator counts the meaningful digits in a measured number and rounds it to a chosen precision. Enter a value to see which digits count, why they count, and how the rounded answer is formed.
SPED math and science support
Turn calculation practice into differentiated instruction
Use the shown rules to support instruction, then enter the student's IEP goals and accommodations manually in the lesson planner. Review and adapt every lesson draft before use.
Count and round sig figs
Enter one number
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Significant figures result
Significant figures
3
Digits: 4, 5, 0
Rounded to 3 sig figs
0.00450
Scientific notation
4.50 × 10^-3
How the sig figs were counted
- 1. Remove the sign and exponent notation, then inspect the coefficient: 0.00450.
- 2. Leading zeros are placeholders, while captive zeros and trailing zeros after a decimal point are significant.
- 3. The significant digits are 4, 5, 0, for a total of 3.
How the number was rounded
- 1. Keep 3 significant digits.
- 2. Round at the 10^-5 place.
- 3. The rounded value is 0.00450, or 4.50 × 10^-3.
Quick rule: Zeros between nonzero digits count. Leading zeros do not. Trailing zeros count when a decimal point or scientific coefficient makes the precision explicit.
How to Use the Sig Fig Calculator
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Review the digits
See which zeros are placeholders and which digits communicate measured precision.
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Choose the precision
Set a target from 1 to 15 significant figures and follow the rounding steps.
Sig Fig Calculator FAQ
What is a sig fig calculator?
A sig fig calculator counts the meaningful digits in a measured number and rounds that number to a chosen number of significant figures.
Are leading zeros significant?
No. Leading zeros only locate the decimal point, so the zeros in 0.00450 are not significant. The digits 4, 5, and the final 0 are significant.
When are trailing zeros significant?
Trailing zeros are significant when a decimal point or scientific notation makes the measured precision explicit. For example, 1500. has four significant figures.
Do zeros between nonzero digits count?
Yes. Captive zeros always count, so 1002 has four significant figures.
How do you round to significant figures?
Start at the first nonzero digit, keep the requested number of digits, and use the next digit to round the last kept digit up or leave it unchanged.