Significant figures calculator
Calculator
The calculator needs JavaScript. The tables below give the same numbers for common cases.
How it is worked out
- Non-zero digits always count; zeros between them count; leading zeros never count.
- Trailing zeros count only when there is a decimal point (0.04500 has 4; 1200 has 2, 1200. has 4).
- Rounded to 3: 0.0450.
| Inputs | Answer |
|---|---|
| Number: 0.04500; Round to this many significant figures: 3 | 0.04500 has 4 significant figures; to 3 it is 0.045. |
| Number: 1200; Round to this many significant figures: 2 | 1200 has 2 significant figures; to 2 it is 1,200. |
| Number: 1200.; Round to this many significant figures: 3 | 1200. has 4 significant figures; to 3 it is 1,200. |
| Number: 3.14159; Round to this many significant figures: 4 | 3.14159 has 6 significant figures; to 4 it is 3.142. |
How to use it
Significant figures are the digits that carry meaning in a measurement. Non-zero digits always count, zeros between them count, leading zeros never count, and trailing zeros count only when there is a decimal point. So 0.04500 has 4, 1200 has 2 and 1200. has 4.
The calculator counts the significant figures in what you typed and also rounds the value to the number you choose. Type the number as text so trailing zeros are kept.
Frequently asked questions
How many significant figures does 0.04500 have?
4: the digits 4, 5, 0 and 0. The leading zeros do not count.
Do trailing zeros count?
Only if the number has a decimal point: 100.0 has 4, while 100 has 1.
How do I round to 3 significant figures?
Keep the first three significant digits and round on the fourth.
Method: standard arithmetic shown step by step; no outside data is used. Checked 2026-11-12.
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General information only. Results are plain arithmetic on the numbers you enter; check anything important (money, health, school work) against your own records or the official source.