Back to Sig Fig Calculator
Significant Figures Counter
Instantly count significant figures in any number. Our sig fig counter highlights each digit and shows you exactly which ones are significant and why.
Count Significant Figures
Enter a number to see how many significant figures it has
Try These Examples
Click any number to count its sig figs
📖 How to Use This Sig Fig Counter
1
Type or paste any number into the input box
2
Click "Count" or press Enter
3
See which digits are significant (green) and the total count
The 5 Rules for Counting Significant Figures
1
Non-zero digits are ALWAYS significant
2
Zeros between non-zero digits are significant
3
Leading zeros are NOT significant
4
Trailing zeros after decimal ARE significant
5
Trailing zeros without decimal are ambiguous
Common Tricky Examples
These numbers often confuse students
| Number | Sig Figs | Why? |
|---|---|---|
| 100 | 1 | Trailing zeros without decimal = NOT significant |
| 100. | 3 | Decimal point makes all digits significant |
| 1000 | 1 | Same rule: trailing zeros without decimal |
| 3.0 | 2 | Trailing zero after decimal IS significant |
| 2.0 | 2 | The .0 indicates measured precision |
| 5.0 | 2 | Two sig figs, not one! |
| 0.00340 | 3 | Leading zeros don't count, trailing does |
| 5.007 | 4 | Zeros between non-zeros are significant |
Frequently Asked Questions
How do I count sig figs in a number?
Enter any number in the input box above and click 'Count'. Our sig fig counter will highlight which digits are significant (green) and which are not (gray), plus show you the total count.
How many sig figs in 100?
100 has 1 significant figure. The trailing zeros are NOT significant because there's no decimal point. To show 3 sig figs, write '100.' with a decimal point.
How many sig figs in 3.0?
3.0 has 2 significant figures. The trailing zero after the decimal point IS significant because it indicates the measurement was precise to the tenths place.
Why does my number show fewer sig figs than I expected?
Trailing zeros without a decimal point are considered ambiguous and not counted as significant. Add a decimal point (e.g., 100.) or use scientific notation (1.00e2) to indicate more precision.
Need to perform calculations with sig figs?
Use the Full Sig Fig Calculator