Online Significant Figures Calculator
Round any number to a chosen number of significant figures, with support for decimals and scientific notation, and copy the result instantly.
Answer
3.66
What Is This Tool?
The Significant Figures Calculator rounds a number to the number of significant figures you choose. You enter a value and how many significant figures you want, click Calculate, and see the rounded result — for example, 3.657 rounded to 3 significant figures becomes 3.66. It correctly handles rounding that carries into a new place, accepts decimals and scientific notation, and shows the expanded form alongside scientific results so you can copy whichever you need.
How to Use This Tool?
- Enter the number you want to round.
- Enter how many significant figures you want to keep.
- Click the Calculate button to see the rounded result.
- Click the copy icon to copy the result to your clipboard.
Key Features
- Rounds a number to a chosen count of significant figures, from 1 to 15.
- Correctly handles rounding that carries into a new digit, such as 9.99 to 2 figures giving 10.
- Accepts plain decimals as well as scientific notation like 3.657e4.
- Shows the expanded decimal form next to scientific-notation results.
- Includes a one-click copy button to place the rounded value on your clipboard.
Examples
- 3.657 rounded to 3 significant figures gives 3.66.
- 3657 rounded to 2 significant figures gives 3700.
- 0.0036570 rounded to 3 significant figures gives 0.00366.
- 9.99 rounded to 2 significant figures gives 10.
Common Use Cases
- Reporting measurements to the precision required in a lab.
- Rounding results in chemistry, physics, or engineering work.
- Tidying long decimal outputs to a consistent precision.
- Preparing values for tables or reports at a fixed significance.
- Teaching or practicing how to round to significant figures.
Tips & Best Practices
- Choose the number of significant figures that matches the precision you need.
- Use scientific notation when you want the precision to be unambiguous.
- Remember that trailing zeros in a whole-number result can look ambiguous in fixed notation.
- Check the expanded form shown for scientific inputs to confirm the magnitude.
- Copy the result directly from the tool to avoid transcription mistakes.
Limitations
- Rounds one number at a time, not a list or batch.
- The number of significant figures must be a whole number from 1 to 15.
- Whole-number results in fixed notation can be ambiguous about which trailing zeros are significant.
- It rounds to significant figures but does not count them for you.
Frequently Asked Questions
- How does it round to significant figures?
- It keeps the requested number of significant digits, rounds the next digit, and restores the original magnitude.
- How many significant figures can I request?
- Any whole number from 1 to 15.
- Does it work with scientific notation?
- Yes. It accepts forms like 3.657e4 and also shows the expanded decimal value.
- What does the "or" in the result mean?
- For scientific inputs it shows the rounded value and its expanded decimal form, separated by "or".
Key Terminology
- Significant figures
- The digits in a number that carry meaningful information about its precision.
- Rounding
- Adjusting a number to a nearby value with fewer digits at a chosen precision.
- Scientific notation
- Writing a number as a coefficient times a power of ten, such as 3.657e4.
- Coefficient
- The leading number in scientific notation that carries the significant figures.
- Place value
- The value a digit holds based on its position, such as tens or hundredths.