About Round to Significant Figures
This calculator rounds a number to the number of significant figures you choose and shows the result both as plain digits and in scientific notation. It is free, needs no sign-up and runs in your browser, so nothing you enter is uploaded.
The page opens on 34567.89 rounded to 3 significant figures. Count three digits from the first non-zero digit: 3, 4, 5. The next digit is 6, so the 5 rounds up. The answer is 34600, or 3.46 × 10^4.
Leading zeros are skipped when counting: 0.0045678 to 2 figures is 0.0046. If you ask for more figures than the number has, zeros are added, so 3 to 4 figures is 3.000.
How to use Round to Significant Figures
- Choose Count, Round, Arithmetic or Scientific notation.
- Type the number exactly as it was measured, keeping any trailing zeros: 0.00450, 1200, 1.20e3.
- For rounding, set how many significant figures to keep. For arithmetic, type the second number and choose the operation.
- Read the answer, then open the digit-by-digit reasons or the steps.
- For a whole number that ends in zeros, use the switch to say whether those zeros were measured.
Features
- Digit-by-digit rule explanation: leading, non-zero, captive and trailing zeros.
- Round to any number of significant figures from 1 to 50, half up.
- Add and subtract by decimal places, multiply and divide by significant figures.
- Scientific notation that keeps exactly the significant figures.
- E-notation input such as 1.20e3 and 4.5 x 10^-3.
- A clear note on the ambiguity of trailing zeros in whole numbers, with a switch.
- Exact decimal arithmetic, no floating-point surprises.
Rounding steps
Find the first non-zero digit, keep n digits from it, and look at the next digit.
34567.89 -> keep 3, 4, 5 | next digit 6 >= 5 -> 346 -> 34600Worked examples
34567.89 to 3 sig figs gives 34600
Next digit 6, so round up.
0.0045678 to 2 sig figs gives 0.0046
Leading zeros do not count.
Privacy: how it works
- Everything is calculated by code running in your browser tab. The numbers you enter are not sent to Ulkaa or to any other server, and there is nothing to sign in to.
Tips
- Write whole numbers that end in zeros in scientific notation, 1.20 × 10³, so nobody has to guess how many figures you meant.
- Keep extra digits in intermediate steps and round only the final answer.
- For a mixed calculation, apply the multiply rule and the add rule to each step separately and round at the end.
Frequently asked questions
Is it really free?
Yes. There is no price, no trial and no credit card. Ulkaa Tool does the work with your own device, so there is no server bill to pass on to you.
Do I need an account?
No. There is no sign-up and no login. Open the page and use it. An Ulkaa account is not needed for anything on this tool.
Does it run in my browser?
Yes. Numbers are processed by code running in your browser tab, on your own device.
Is my data uploaded?
No. Numbers are never sent to Ulkaa or to anyone else. You can check this yourself by watching the Network tab in your browser developer tools while you use the tool.
How do I round to significant figures?
Start counting at the first non-zero digit, keep the number of digits asked for, and round up if the next digit is 5 or more.
What does 3 significant figures of 999.9 give?
1000, written as 1.00 × 10³. Rounding up carried through the nines and added a digit.
More Significant Figures Calculator pages
- Significant Figures CalculatorType a measurement to count its significant figures, round it, calculate with it or write it in scientific notation.
- Significant Figures AdditionEnter two numbers to add or subtract them and keep the right precision.
- Significant Figures MultiplicationEnter two numbers to multiply them and keep the right significant figures.
- Significant Figures DivisionEnter two numbers to divide them and keep the right significant figures.
- Scientific Notation and Sig FigsType a number and get its scientific notation with the right number of digits.
- Significant Figures in Whole NumbersWhole numbers that end in zeros are ambiguous. See how many figures 1200 has and how to say what you mean.