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Rounding Calculator — Decimals, Sig Figs & Multiples

Round any number to a set number of decimal places, a set number of significant figures, or the nearest multiple of a value you choose.

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📝 Enter a Number

📊 Result

Enter a number and choose a rounding mode
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Disclaimer: This tool performs standard mathematical calculations for educational and reference purposes. Always double-check results independently for graded coursework, exams, or safety-critical applications.

How Rounding Works

Rounding replaces a number with a simpler, nearby value while keeping it close to the original. This calculator uses the "round half up" convention throughout: when the part being dropped is exactly halfway, the last kept digit rounds upward. Which type of rounding you need depends on the situation.

Decimal Places

Rounding to N decimal places keeps exactly N digits after the decimal point and drops the rest, adjusting the last kept digit based on what follows it. This is the everyday rounding most people learn first — useful for currency, measurements, and general precision limits.

Significant Figures

Rounding to N significant figures keeps N meaningful digits starting from the first non-zero digit, no matter where the decimal point falls. This means large numbers get rounded to the left of the decimal point (12,345 to 2 sig figs is 12,000) while small decimals get rounded further right (0.012345 to 2 sig figs is 0.012). Scientists and engineers favor significant figures because they communicate how precisely a value was actually measured.

Nearest Multiple

Rounding to the nearest multiple of M snaps a number to the closest value that's evenly divisible by M — for example, rounding to the nearest multiple of 5 or 10. This is handy for scheduling in fixed time blocks, pricing in fixed increments, or packaging quantities in fixed batch sizes.

Worked Examples

Frequently Asked Questions

Decimal places count digits after the decimal point only, so 1234.5678 to 2 decimal places is 1234.57. Significant figures count meaningful digits starting from the first non-zero digit, regardless of where the decimal point sits, so 1234.5678 to 2 significant figures is 1200. Significant figures are more common in science because they reflect measurement precision, not just position.
"Round half up" is the everyday rule most people learn in school: if the digit being dropped is 5 or more, the last kept digit increases by one. This calculator uses that convention. Other fields sometimes use "round half to even" (banker's rounding) instead, which reduces long-run bias when rounding huge datasets, but round half up is the standard default for general-purpose use.
Rounding to a multiple is useful whenever your answer has to land on a fixed step size rather than a fixed number of decimals — pricing items in 5-cent increments, scheduling in 15-minute blocks, or packing items in boxes of 12. Instead of chopping decimals, you're snapping the number to the closest allowed step.
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