Significant Figures Calculator
Count significant figures in any number, round to N sig figs, convert to scientific notation, and apply sig fig rules for arithmetic operations.
Significant Figures Count
—
Rounded to N Sig Figs —
Scientific Notation —
Extended More scenarios, charts & detailed breakdown ▾
Sig Figs Count
—
Scientific Notation —
Professional Full parameters & maximum detail ▾
Digit Analysis
Digit Analysis —
Trailing Zeros Analysis —
Addition/Subtraction Rule
Addition Result (sig fig rule) —
Addition Explanation —
How to Use This Calculator
- Enter a number in the input field to instantly count its significant figures.
- Enter N to round the number to that many significant figures.
- Use the Round to N tab for rounding with scientific notation output.
- Use the Arithmetic tab to multiply or divide two numbers with correct sig fig handling.
- The Professional tab provides digit-by-digit analysis and addition/subtraction decimal-place rules.
Formula
Rounding to N sig figs: Find the Nth significant digit, apply standard rounding on the (N+1)th digit.
Scientific notation: a × 10ⁿ where 1 ≤ |a| < 10
Multiplication/Division: result sig figs = min(sig figs of inputs)
Example
0.004560 → 4 sig figs (4,5,6,0). Round 3.14159 to 3 sig figs → 3.14. 2.5 × 3.42 = 8.55 → 2 sig figs → 8.6.
Frequently Asked Questions
- Significant figures (sig figs) are the meaningful digits in a number that carry measurement precision. The number 0.00420 has 3 sig figs (4, 2, 0 — the trailing zero after decimal is significant).
- Rules: (1) All non-zero digits are significant. (2) Zeros between non-zeros are significant. (3) Leading zeros are NOT significant. (4) Trailing zeros after a decimal ARE significant. (5) Trailing zeros without a decimal may or may not be significant.
- Identify the Nth significant digit, then round normally. To round 0.004567 to 3 sig figs: the 3rd sig fig is 5, the next digit is 6 ≥ 5 so round up → 0.00457.
- For multiplication and division, the result should have the same number of significant figures as the measurement with the fewest sig figs. 2.5 × 3.42 = 8.55 → round to 2 sig figs → 8.6.
- For addition and subtraction, the result should have the same number of decimal places as the measurement with the fewest decimal places. 12.52 + 349.0 + 8.24 = 369.76 → round to 1 decimal → 369.8.