Significant Figures Calculator - Count & Round Sig Figs Instantly
Significant Figures Count:
5
Rounded Result:
123
How Significant Figures Work
Input Number
Enter any decimal or integer
Apply Rules
Follow sig fig counting rules
Count Digits
Count significant digits
Significant Figures Rules & Formulas
Counting Rules:
- • All non-zero digits are significant
- • Zeros between non-zero digits are significant
- • Leading zeros are not significant
- • Trailing zeros in decimals are significant
- • Trailing zeros in whole numbers without decimal are not significant
Rounding Formula:
rounded = round(n × 10^(sf-1-magnitude)) / 10^(sf-1-magnitude)
where sf = significant figures, n = number
Significant Figures Examples Table
| Number | Sig Figs | Rounded to 3 | Rounded to 2 | Scientific Notation |
|---|---|---|---|---|
| 123.456 | 6 | 123 | 1.2e+2 | 1.23456e+2 |
| 0.00789 | 3 | 0.00789 | 0.0079 | 7.89e-3 |
| 1200 | 2 | 1.20e+3 | 1.2e+3 | 1.2e+3 |
| 0.0120 | 3 | 0.0120 | 0.012 | 1.20e-2 |
| 5000.0 | 5 | 5.00e+3 | 5.0e+3 | 5.0000e+3 |
| 0.000456 | 3 | 0.000456 | 0.00046 | 4.56e-4 |
| 98765 | 5 | 9.88e+4 | 9.9e+4 | 9.8765e+4 |
| 0.10200 | 5 | 0.102 | 0.10 | 1.0200e-1 |
| 7.000 | 4 | 7.00 | 7.0 | 7.000e+0 |
| 0.00001 | 1 | 1.00e-5 | 1.0e-5 | 1e-5 |
| 123000 | 3 | 1.23e+5 | 1.2e+5 | 1.23e+5 |
| 0.50400 | 5 | 0.504 | 0.50 | 5.0400e-1 |
| 9.876e4 | 4 | 9.88e+4 | 9.9e+4 | 9.876e+4 |
| 0.000100 | 3 | 0.000100 | 0.00010 | 1.00e-4 |
| 456.78 | 5 | 457 | 4.6e+2 | 4.5678e+2 |
Significant Figures Progression Chart
123
0.00456
1200
0.0120
5.67e4
100.0
Practice Problems
Problem 1:
How many sig figs in 0.00450?
Solution: 3 sig figs (4, 5, and trailing 0 after decimal)
Problem 2:
Round 123.456 to 4 sig figs
Solution: 123.5 (round up the 4th digit)
Problem 3:
How many sig figs in 1200?
Solution: 2 sig figs (trailing zeros without decimal are not significant)
Problem 4:
Round 0.008765 to 2 sig figs
Solution: 0.0088 (8 and 7, round up)
Problem 5:
How many sig figs in 5.000?
Solution: 4 sig figs (all digits including trailing zeros after decimal)
Daily Uses of Significant Figures
Scientific measurements require proper precision reporting
Engineering calculations need accurate significant digit handling
Laboratory results must show measurement uncertainty
Financial calculations require appropriate decimal precision
Quality control processes use sig figs for tolerance limits