Round any number to a chosen precision and rounding rule. You can round to a number of decimal places or to the nearest multiple (5, 10, 100, 0.25, and so on), choosing the method that fits — from everyday half-up to banker’s rounding for unbiased totals.
How it works
You set a target — either a number of decimal places or a multiple to snap to — and a method. The tool scales the value to that target, applies the rule, then scales back:
- Round half up — the standard rule; halfway values go to the larger number (2.5 → 3).
- Round half to even (banker’s rounding) — halfway values go to the nearest even number (2.5 → 2, 3.5 → 4), avoiding the upward bias half-up accumulates over many figures.
- Ceiling — always round up. Floor — always round down.
- Truncate — drop the extra digits toward zero.
For nearest-multiple mode, the value is divided by the step, rounded, then multiplied back, so 47 to the nearest 10 becomes 50.
Example
Rounding 2.5 to a whole number shows how the method matters:
| Method | 2.5 → | 3.5 → | −2.7 → |
|---|---|---|---|
| Half up | 3 | 4 | −3 |
| Half to even | 2 | 4 | −3 |
| Ceiling | 3 | 4 | −2 |
| Floor | 2 | 3 | −3 |
| Truncate | 2 | 3 | −2 |
Rounding 47 to the nearest multiple of 10 gives 50; to the nearest 0.25, 2.6 becomes 2.5.
Choosing the right method
Each method has a specific use case, and picking the wrong one produces systematic errors:
Round half up is what most people learned in school and what most everyday situations expect. It has a small upward bias: in a large dataset with many exact halfway values (like prices ending in .5), rounding everything up shifts totals slightly high. For most one-off calculations the bias is negligible.
Banker’s rounding (round half to even) was designed for accounting and statistical work precisely to avoid that bias. By sending halfway values to the nearest even number, it distributes rounding errors symmetrically across large datasets — roughly half go up, half go down. IEEE 754 floating-point arithmetic uses this as its default rounding mode, and many financial systems mandate it for this reason.
Ceiling is the right choice when you must not fall short. Buying boxes to pack items — you must never have too few, so always round up to the nearest whole box. Calculating time slots — a 90-minute task rounded to 1-hour intervals requires 2 slots if you must not run over.
Floor is the right choice when you must not exceed. Dividing money into equal portions without creating a surplus — floor gives each person an integer amount and leaves no fractional cents unaccounted for. Computing how many whole items fit within a capacity limit.
Truncate differs from floor for negative numbers. Both floor and truncate give the same result for positive numbers, but truncate always moves toward zero, while floor always moves toward negative infinity. For −2.7: truncate gives −2, floor gives −3. Truncate is the natural choice when you want to discard fractional parts without worrying about sign.
Nearest-multiple rounding
Nearest-multiple mode is useful when values need to snap to a grid:
- Nearest 5 or 10 — rounding prices, scores, or measurements to tidy intervals. 47 → 50 (nearest 10), 53 → 55 (nearest 5).
- Nearest 0.25 — quarter-steps, common in financial or musical contexts. 2.6 → 2.5; 2.8 → 3.0.
- Nearest 0.01 — currency rounding to cents or pence.
- Nearest 15 — meeting slot rounding (a 22-minute event → next 15-minute slot = 30 minutes, using ceiling mode on the multiple).
All rounding runs entirely in your browser; nothing is uploaded.