Sumivo · Mathematics
Significant Figures Calculator
Count the significant figures in your original number. Optionally round to a chosen precision and see scientific notation. Plain-integer trailing zeros are excluded by default; use the switch below to include them, or write 1.50e3 to specify three figures.
01 / inputs
02 / result
SIGNIFICANT FIGURES IN INPUT
3
- Scientific notation
- 4.50 × 10^-3
- E notation
- 4.50E-3
- Decimal value
- 0.00450
- Output precision
- Count only
Calculation trace
- 0.00450: 3 significant figuresCount the original written digits
- No change to the numeric valuePreserve the value
- 4.50 × 10^-3 = 4.50E-3Display the resulting precision explicitly
Leading zeros do not count; nonzero digits, interior zeros and written trailing zeros in a decimal or E-notation coefficient count.
How it works
Count the original written coefficient before rounding. Leading zeros do not count; nonzero digits and zeros between them count. Trailing zeros count when a decimal point or E notation makes them explicit. Plain-integer trailing zeros follow the selected assumption. Optional precision rounds once at the place determined by the first nonzero digit and requested count, using the exact rounding engine. Half-up ties go away from zero; half-even ties keep an even retained digit. Scientific notation preserves the requested trailing zeros, including after a carry such as 999.9 becoming 1.0 × 10^3 at two figures.
Assumptions & limits
- Plain integers such as 1500 default to excluding trailing zeros (2 figures). The switch includes them (4 figures). Write 1.5e3, 1.50e3 or 1.500e3 to unambiguously specify 2, 3 or 4 figures. An explicit decimal point, including 1500., counts written trailing zeros; E notation also makes coefficient trailing zeros explicit.
- All-zero input has an indeterminate significant-figure count here. It is displayed as 0 × 10^0 even when precision is requested; the tool does not infer measurement uncertainty from zero-only notation. Exact counted quantities may have unlimited precision, which cannot be inferred from a digit string.
- Accepts decimal or e/E strings up to 4096 characters and 2000 coefficient digits. Input and normalized exponents are limited to −1000 through 1000, including after rounding. Requested precision is 1–100, or blank for counting without rounding. Commas, expressions and fractions are rejected.
- The displayed count describes the input, not the rounded output. Padding with requested zeros is formatting and does not create measurement information. Decimal output expresses value; scientific notation expresses the chosen precision.
FAQ
- How do you count significant figures?
- Start at the first nonzero digit. Count every following digit, including interior zeros and decimal trailing zeros. For a plain integer without a decimal point, this tool excludes trailing zeros by default, and shows a switch to include them.
- How many significant figures are in 0.00450?
- There are 3: 4, 5 and the final 0. The leading zeros only locate the decimal point. The equivalent scientific notation is 4.50 × 10^-3.
- Does 1500 have two, three or four significant figures?
- The notation alone is ambiguous. This tool defaults to 2 or can count all 4 with the switch. Use 1.5e3 for 2, 1.50e3 for 3 or 1.500e3 for 4. These strings have the same value but express different precision.
- How do I round to three significant figures?
- Enter 3 in the optional precision field. Keep three digits beginning at the first nonzero digit, then use the discarded remainder to round. For example, 0.012345 becomes 1.23 × 10^-2. Choose half-up for ties away from zero or half-even for even ties.
- Are significant figures the same as decimal places?
- No. Decimal places count positions after the decimal point, while significant figures begin at the first nonzero digit. Thus −0.0100 has 4 decimal places but 3 significant figures. In 1.20e3, the coefficient has 3 significant figures; the exponent changes scale, not precision.
Related calculators
SOURCES
- OpenStax (Rice University)Chemistry 2e — 1.5 Measurement Uncertainty, Accuracy, and Precision ↗
Section 1.5: significant figures in measurements, leading and interior zeros, ambiguous integer trailing zeros, and scientific notation to express precision. Zero-count convention, selectable tie modes and input limits are stated by this calculator.
Accessed 2026-10-02