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Rounding Calculator

Round any number to a chosen number of decimal places or to the nearest 10, 100, or 1000, using round-half-up, floor (down), or ceiling (up).

Rounded result
3.14

Round (half up) of 3.14159 to 2 decimal places = 3.14.

Quick answer

Rounding replaces a number with a nearby simpler value. To round to a place, look at the next digit: 5 or more rounds up, less than 5 rounds down. 3.14159 to 2 decimal places is 3.14; 47 to the nearest 10 is 50. This tool also offers floor (always down) and ceiling (always up) modes.

Formula & method

The tool divides the number by the chosen step (10^−places for decimals, or 10/100/1000 for nearest-multiple), applies the selected mode — Math.round for half-up, Math.floor for down, Math.ceil for up — then multiplies back by the step. Floating-point dust is cleaned so results display exactly.

Examples

Example 1: Decimal places
Input
3.14159 to 2 dp (round)
Result
3.14
Why
The third decimal is 1 (< 5), so the second decimal stays 4.
Example 2: Nearest 10
Input
47 to nearest 10 (round)
Result
50
Why
47 is closer to 50 than to 40, so it rounds up.
Example 3: Floor vs ceiling
Input
3.99 floor / 3.01 ceil (nearest 1)
Result
3 / 4
Why
Floor always rounds down to 3; ceiling always rounds up to 4.

When to use this tool

  • Presenting money, measurements, or statistics to a sensible precision.
  • Rounding totals to the nearest 10, 100, or 1000 for estimates.
  • Forcing values up (ceiling) or down (floor) for capacity or budgeting.

Common mistakes

  • Rounding step by step (e.g. 2.45 → 2.5 → 3) instead of rounding once to the target place.
  • Assuming floor and round are the same — floor always goes down, even for .99.
  • Mixing up decimal places with significant figures, which count from the first non-zero digit.

Frequently asked questions

How does standard rounding work?

Look at the digit just past the place you are rounding to: if it is 5 or more, round up; if it is less than 5, round down. This tool uses round-half-up by default.

What is the difference between floor and ceiling?

Floor always rounds down to the lower multiple; ceiling always rounds up to the higher one, regardless of the next digit.

Can I round to the nearest 10 or 100?

Yes. Choose the 'round to' option for the nearest 1, 10, 100, or 1000.

How is this different from significant figures?

Decimal places count digits after the point; significant figures count from the first non-zero digit. Use the significant figures calculator for the latter.

Does it handle negative numbers?

Yes. Note that floor of a negative number moves toward more negative, and ceiling moves toward zero.

Is the result exact?

Yes. The tool removes binary floating-point artefacts so the displayed value is clean.

Sources & references

External references open in a new tab. We are independent and not affiliated with these organizations.

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  • ✓ No sign-up required
  • ✓ Runs entirely in your browser — nothing is uploaded.
  • ✓ Formula and method shown above
Last updated: How we calculateReport a correctionDisclaimer

Provided “as is” for general information only — results may be inaccurate, so verify before you rely on them. No warranty; use at your own risk.

Built and reviewed by HIFreeTools against the formula shown above and any authoritative references cited on this page. See our methodology and editorial standards.

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