Significant Figures Calculator
Enter a number or an expression (e.g.,
5.13*3.78)Results
Decimal notation:—
Number of significant figures:—
Number of decimals:—
Scientific notation:—
E notation:—
Step-by-step output
SF = significant figure
Rules Used by This Calculator
- All non-zero digits are significant.
- Zeros between non-zero digits are significant.
- Leading zeros before the first non-zero digit are not significant.
- Trailing zeros are significant only when there is a decimal point.
- Rounding uses “half-up” (5 rounds up).
- Add/Subtract → round the final result to the fewest decimal places among inputs.
- Multiply/Divide → round the final result to the fewest significant figures among inputs.
Use this Significant Figures Calculator to count significant figures, round values, evaluate supported expressions, and display results in decimal, scientific, or E notation.
Significant Figure Rules
- All non-zero digits are significant.
- Zeros between non-zero digits are significant.
- Leading zeros are not significant.
- Trailing zeros after a decimal point are significant.
For calculations:
Addition and subtraction: round to the fewest decimal places among the inputs.
Multiplication and division: round to the fewest significant figures among the inputs.
Example
The number 0.00450 has 3 significant figures: 4, 5, and the trailing zero.
For:
5.13 × 3.78 = 19.3914
Both inputs have 3 significant figures, so the result is reported as:
19.4
Important Note
Significant figures are a convention for reporting measurement precision. Laboratory, engineering, regulatory, or publication requirements may specify different rounding or uncertainty rules.