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Significant Figures Rounding Calculator
Round any number to your desired number of significant figures. Our rounding tool handles trailing zeros correctly using scientific notation when needed.
Sig Fig Rounding Tool
Round any number to a specific number of significant figures
Try These Examples
Click to see how rounding works
📖 How to Round Significant Figures
1
Enter the number you want to round
2
Select how many significant figures you want (1-6)
3
Click "Round" to see the result
Rounding Rules for Chemistry
↑
If digit ≥ 5, round UP
Example: 2.35 → 2.4 (to 2 SF)
↓
If digit < 5, round DOWN
Example: 2.34 → 2.3 (to 2 SF)
⚠
Trailing zeros need special handling
9876 → 9900 (2 SF) is ambiguous, so we write 9.9×10³
Rounding Examples Table
See how different numbers round to various sig figs
| Original | Target SF | Result | Note |
|---|---|---|---|
| 123.456 | 3 | 123 | Keep 3 most significant digits |
| 123.456 | 4 | 123.5 | Round 4th digit (5 rounds up) |
| 0.004567 | 2 | 0.0046 | Leading zeros don't count |
| 9876 | 2 | 9900 or 9.9e+3 | Trailing zeros need scientific notation |
| 2.35 | 2 | 2.4 | 5 rounds up (standard rule) |
| 1000 | 2 | 1.0e+3 | Scientific notation shows exact precision |
Frequently Asked Questions
How do I round to significant figures?
Enter your number, select how many sig figs you want (1-6), and click 'Round'. The tool will show you the properly rounded result, using scientific notation when needed to avoid ambiguity.
Why does my result show in scientific notation?
When rounding creates trailing zeros (like 9876 → 9900 with 2 sig figs), the result is ambiguous. Scientific notation (9.9e+3) clearly shows exactly 2 significant figures.
What's the rule for rounding when the digit is 5?
In standard scientific rounding, if the digit to drop is 5 or greater, round up. So 2.35 rounded to 2 sig figs becomes 2.4.
Can I round to more sig figs than the original number has?
Technically yes, but it doesn't add real precision. If you have 12 (2 sig figs) and round to 4 sig figs, you get 12.00, but those extra zeros don't represent actual measured precision.
Need to perform calculations with automatic sig fig rounding?
Use the Full Sig Fig Calculator