Significant Figures Calculator: Round to Sig Figs, Scientific Notation, Engineering Notation and Sig Fig Rules
Round correctly and write numbers in scientific notation.
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How this calculator works
Choose rounding, scientific notation, engineering notation or a calculation.
Enter the number and how many figures or places to keep.
For a calculation enter both numbers with their significant figures or decimal places and the answer is given to the right precision.
Formulas used
- x = a\times10^{n},\ 1\le|a|<10
- x = a\times10^{3k}
- sf_{result} = \min(sf_1, sf_2)\ (\times,\div)
- dp_{result} = \min(dp_1, dp_2)\ (+,-)
Worked example
With the default numbers in the calculator above:
- Position of the first non-zero digit (the power of ten): 5
- Rounded to 4 significant figures: 123500
- Error from rounding: 43.211 (0.035001 percent)
Change the numbers in the calculator to see the full working, every step, for your own case.
A second worked example
A different case, with these numbers: What do you want? Scientific notation (standard form).
- Scientific notation (standard form): one non-zero digit before the point: 1.235 x 10^5
- Written in full with the mantissa and exponent: a = 1.2345679, n = 5
- E notation as used on calculators and spreadsheets: 1.235E5
Common questions
How many significant figures does a number have?
Count from the first non-zero digit. Zeros between digits count, trailing zeros after a decimal point count, and leading zeros do not. 0.00450 has 3.
What are the rules for calculations?
When multiplying or dividing keep the fewest significant figures. When adding or subtracting keep the fewest decimal places.
What is scientific notation?
A number written as a times ten to a power, with a between 1 and 10. 123 500 is 1.235 x 10 to the 5.
When should I round?
Only at the end. Keep extra digits in the working.
Related calculators
Got a question about this? Ask an engineering question and get a plain-language answer with references.
Further reading: Any school science or mathematics text (significant figures and standard form).
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