Count and adjust the significant figures of any number or mathematical expression. The calculator displays the decimal notation, scientific notation, E notation, the number of significant figures, and the decimal places.
Significant Figures Calculator
Enter a number or expression (e.g. '5.13*3.78')
How to use the calculator
- In the Number or expression field, enter a number (e.g.
0.00520) or an expression (e.g.5.13*3.78). - Optionally, enter the number of significant figures to round the result.
- The calculator displays the decimal, scientific, and E notation, the total significant figures, and decimal places — with significant digits highlighted.
What are significant figures
Significant figures are the digits of a number that have meaning in terms of precision. The main rules are:
- Leading zeros are NOT significant. E.g.:
0.0045has 2 sig. figs. (4 and 5). - Zeros between digits ARE significant. E.g.:
1.003has 4 sig. figs. - Trailing zeros after the decimal ARE significant. E.g.:
2.50has 3 sig. figs. - Trailing zeros in integers are ambiguous without scientific
notation. E.g.:
1200may have 2, 3, or 4 sig. figs.
Counting examples
| Number | Significant Figures | Reason |
|---|---|---|
| 0.00520 | 3 | 5, 2, 0 (trailing zero after decimal is sig.) |
| 1.003 | 4 | 1, 0, 0, 3 (zeros between digits) |
| 100 | 1–3 | Ambiguous without decimal point or scientific notation |
| 3.456 × 10² | 4 | 3, 4, 5, 6 |
| 0.000067 | 2 | 6 and 7 (leading zeros don't count) |
Rounding to n significant figures
To round 3.456 to 2 significant figures:
- The 2nd significant figure is 4.
- The next digit is 5 → round up.
- Result: 3.5
For 0.004567 with 3 sig. figs.: result = 0.00457.
Frequently asked questions
What are significant figures?
They are the digits of a number that express its precision. They include all non-zero digits, zeros between digits, and trailing zeros after the decimal point. They do not include leading zeros used only to position the decimal.
How do I count significant figures?
1) Leading zeros do NOT count. 2) Zeros between digits DO count. 3) Trailing zeros after the decimal DO count. 4) Trailing zeros in integers without a decimal are ambiguous. Example: 0.00520 → 3 sig. figs. (5, 2, 0).
How do I round to n significant figures?
Locate the nth significant figure from the left and round from that point. Example: 3.456 to 2 sig. figs. → 3.5; 0.004567 to 3 sig. figs. → 0.00457.
What is the difference between significant figures and decimal places?
Decimal places count the digits after the decimal point. Significant figures count the meaningful digits of the number. E.g. 0.0045 has 4 decimal places but only 2 significant figures.
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