Round to 4 Significant Figures Calculator
Count the significant figures in any number with every digit classified by rule, or round a number to 1–15 significant figures with exact string-based math.
Processed entirely in your browser — nothing you enter here is ever uploaded.
Result
About this tool
This page opens the sig fig calculator preset to round to 4 significant figures, a precision fine enough for engineering constants and most tabulated physical data — π at four figures is 3.142, e is 2.718.
The fifth significant digit makes the call. 3.14159 keeps 3, 1, 4, 1 and the next digit is 5, so the last kept digit rises: 3.142. Carries chain cleanly through nines: 999.97 to four figures rolls over to 1000, and the tool notes that this particular result hides its own precision — written plainly, 1000 could mean anything from 1 to 4 significant figures.
That is exactly when the scientific notation option earns its place: 1.000 × 10³ says four significant figures and nothing else. The rounding operates on the digits you typed, so no floating-point representation error can creep into the last figure. All of it runs locally in your browser.
Example. The number 0.00450 is classified as three significant figures.
Limit. Rounding is offered for 1 through 15 significant figures and will not invent digits past the supplied numeral.