Sig Fig Rounding Calculator
Use this free sig fig rounding calculator to round any number to the desired number of significant figures. Enter your number and the target sig figs to get an instantly rounded result with a step-by-step breakdown.
Enter Values
The number you want to round
How many sig figs to keep
Result
Enter values above and click Calculate to see your result.
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Formula
Identify the Nth significant digit, look at the next digit to determine whether to round up or keep, then replace all remaining digits with zeros or truncate after the decimal.
Worked Example
How to Round to Significant Figures
- 0.004567 rounded to 2 sig figs is 0.0046 (leading zeros do not count)
- 1234 rounded to 2 sig figs is 1200 (trailing digits replaced with zeros)
- 9.8756 rounded to 4 sig figs is 9.876 (standard rounding applies to the cutoff digit)
- This method is essential in science and engineering where measurement precision matters
Sig fig rounding is used throughout chemistry, physics, and engineering to ensure calculated results do not imply more precision than the original measurements support.
You can also calculate changes using our Sig Fig Rules Calculator, Sig Fig Scientific Notation Calculator or Sig Fig Multiplication Calculator.
Frequently Asked Questions
What are significant figures?
Significant figures (sig figs) are the meaningful digits in a number that contribute to its precision. They include all non-zero digits, zeros between non-zero digits, and trailing zeros after a decimal point.
How do I round to 3 significant figures?
Find the third significant digit, look at the fourth digit: if it is 5 or greater, round the third digit up; if it is less than 5, keep the third digit as is. Replace all digits after the third significant digit with zeros (or truncate after the decimal).
Do leading zeros count as significant?
No. Leading zeros (zeros before the first non-zero digit) are placeholders only. For example, 0.0045 has 2 significant figures, not 4.
When should I use sig fig rounding vs decimal place rounding?
Use sig fig rounding when dealing with measured quantities in science, where the number of meaningful digits matters regardless of magnitude. Use decimal place rounding for financial calculations or when precision is tied to a specific decimal position.
What happens if I round to more sig figs than the number has?
You would add trailing zeros after the decimal point. For example, rounding 1.5 to 4 sig figs gives 1.500, explicitly showing the precision.
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