Sig Fig Calculator (Significant Figures)
Count significant digits, round numbers, and perform arithmetic with sig fig precision rules. Your work stays on this device whenever possible.
How to use Sig Fig Calculator (Significant Figures)
- Pick a mode in 'Tool Mode': 'Count & Identify Significant Figures', 'Round to N Significant Figures' or 'Sig Fig Operations (+, −, ×, ÷)'.
- In count mode type a value such as 0.004500, 120.0 or 6.022 × 10^23 into 'Enter Number or Scientific Notation'.
- In round mode fill 'Number to Round' and 'Target Sig Figs', and tick the Banker's Rounding box for half-to-even ties.
- In operations mode enter 'Value 1', choose the operator, and enter 'Value 2'.
- Press 'Calculate' and read the highlighted digits, the applied rule, or the limited result; 'Load Sample' fills a demonstration value.
Worked example
Choose 'Sig Fig Operations', enter Value 1 = 145.8, the × operator and Value 2 = 2.30. The first term has 4 significant figures and the second has 3, since a trailing zero after a decimal point counts. The product 335.34 is limited to 3 figures, so the result box shows 335 and the precision limit reads 3 sig figs.
When to use this tool
- A physics student reporting a density from a mass of 145.8 g and a volume measured to three figures.
- Preparing lab-report tables where every entry must show the correct number of figures.
Important limitations
Counting adheres to standard scientific rules: leading zeros are never significant, while trailing zeros without a decimal point are treated as ambiguous. Exact counts possess infinite significant figures and should not limit experimental calculations.
Comparing alternatives
Other options for sig fig calculator (significant figures) include CalculatorSoup, Omni Calculator, SigFigCalculator.org.
ToolkitPoint is not affiliated with those services.
Frequently asked questions
How are trailing zeros in whole numbers treated?
1200 counts as 2 significant figures because trailing zeros without a decimal point are treated as place holders. Write 1200. with a trailing point, or 1.200e3, to make all four digits count.
Why does addition ignore significant figures?
Sums and differences are limited by decimal places, not figure counts. 12.11 + 0.3 is limited to one decimal place, so the tool returns 12.4. Only multiplication and division use the fewest-figures rule.
What does the Banker's Rounding box change?
It rounds an exact tie to the even digit, so 2.5 to one figure gives 2 and 3.5 gives 4. Standard mode uses toPrecision, so a stored value slightly below a tie, such as 1.005, rounds down.
Can I mark a number as exact?
No. Every typed value is treated as a measurement, and there is no exact-number flag. For a count like 3 apples times 2.5 kg, set the answer's figures by hand from the measured term only.
Which scientific formats does it read?
It reads forms like 3.00e8, 3.00 × 10^8 and 3.00x10^8. Only the mantissa digits are counted, so each of those has three significant figures regardless of how large the exponent is.