SigFigCalculator
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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

What this significant figures counter accepts

Use standard numbers or E notation. For x 10^n notation, type the same value as E notation.
3500
Whole numbers

Usually 2 sig figs by default

35.0056
Decimals

Zeros between non-zero digits count

3.5e3
E notation

Equivalent to 3.5 x 10^3

0.00340
Small measurements

Leading zeros ignored, final zero counted

Tricky sig fig counter examples

These are the inputs students most often check when counting significant figures.
0.020
2

The 2 and the final decimal zero are significant.

0.00450
3

Leading zeros are placeholders; 4, 5, and 0 count.

100
1 by default

Without a decimal point, the zeros are ambiguous.

100.0
4

The decimal point makes every trailing zero significant.

2.500 x 10^3
4

Only the coefficient 2.500 controls the count. Enter it as 2.500e3.

12 eggs
exact

A counted value is exact, so it is not limited by sig figs.

Counter
Use this page when you only need to count significant figures in one number.
Rounding
Use the rounding calculator when you need a number rounded to 1, 2, 3, or more sig figs.
Full calculator
Use the full calculator for addition, subtraction, multiplication, division, and mixed expressions.

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.

More questions about counting sig figs

What is a sig fig counter?

A sig fig counter is a tool that counts the significant figures in a number and shows which digits communicate precision. It is useful for chemistry, physics, lab reports, and homework checks.

How do I count significant figures in 100?

Plain 100 is usually counted as 1 significant figure because the two trailing zeros are ambiguous. Write 100. or 1.00e2 when you need to show 3 significant figures.

Can this counter handle scientific notation?

Yes. Use E notation, such as 3.20e4 or 1.00e2. In scientific notation, the coefficient controls the significant figure count and the exponent only changes the scale.

Why are some zeros not significant?

Leading zeros only place the decimal point, so they are not significant. Trailing zeros count when a decimal point or scientific notation shows that the zeros were measured.

Do exact numbers count as significant figures?

Exact numbers are treated as having unlimited significant figures. Counts and defined conversions, such as 12 samples or 100 cm = 1 m, do not limit the final answer.

Related sig fig tools and guides

Round to significant figuresSee more counting examplesCheck exact number rulesPrint a sig figs worksheetCompare decimals and sig figsPractice with instant feedback

Need to perform calculations with sig figs?

Use the Full Sig Fig Calculator