Sig Fig Calculator
Count and round significant figures from the typed number, including decimal zeros, exact numbers, and scientific notation.
At a glance
- Computes
- Significant figure count for a typed number, and that number rounded to a target.
- You supply
- The number as written, its kind, and the target significant figures.
- Use when
- Trailing and leading zeros must be judged from how the number was written.
- Not for
- Rewriting a number into scientific or engineering notation. Scientific Notation Converter
Significant figures
Enter a number
Lexical parser preserves decimal points, trailing zeros, and exponent notation.
- Scientific notation
- Not calculated
- Rounded value
- Only shown in round mode
| Digit | Counts | Reason |
|---|
significant digits are counted from the first nonzero digit, with decimal trailing zeros preserved
How?
How this is calculated
The tool parses the typed string instead of converting it to a JavaScript number. Nonzero digits count, leading zeros do not, zeros between nonzero digits count, and trailing zeros after a decimal point count. Whole-number trailing zeros without a decimal point are ambiguous, so the selected convention is shown.
Exact-number mode reports unlimited significant figures. Round mode keeps the full typed precision until the final display and uses tie-to-even rounding unless half-up is selected.
Formula: significant digits are counted from the first nonzero digit, with decimal trailing zeros preserved
How many significant figures does a number have?
Nonzero digits count, zeros between nonzero digits count, and leading zeros only locate the decimal point. Trailing zeros after a decimal point count because they report precision. A whole number such as 1500 is ambiguous without a decimal point or scientific notation, so the selected trailing-zero convention remains visible instead of being guessed.
How to round to significant figures
Count from the first nonzero digit to the last position being kept, inspect the following digit, and round once. Tie-to-even avoids an upward drift over many rounded measurements; half-up matches the convention used in many school texts. Scientific notation makes intended precision explicit: 1.5e3 has two significant figures while 1.500e3 has four.
Significant figures in arithmetic
Multiplication and division keep the fewest significant figures among measured operands. Addition and subtraction keep the coarsest last significant place. Exact counts and defined factors do not limit precision; append an exclamation mark to mark one exact. The evaluator carries guard digits through the expression and rounds only the final answer, preventing repeated intermediate rounding from accumulating error.
Sources
- OpenStax Chemistry 2e, Measurement Uncertainty, Accuracy, and Precision. OpenStax. Retrieved .
- OpenStax Chemistry 2e, Mathematical Treatment of Measurement Results. OpenStax. Retrieved .
Method last reviewed