Rounding Calculator
Round any number by decimal places, to a nearest unit, or to significant figures.
Rounded to 2 decimal places
Rounding replaces a number with a nearby, simpler value to a chosen precision. 3.14159 rounded to 2 decimal places is 3.14: you keep two digits after the point, then look at the next digit (1). Because 1 is below 5, the kept digits stay the same and the number rounds down.
What rounding is
Rounding trims a number to a target precision while keeping it as close as possible to the original. You decide how precise the answer should be — to a number of decimal places, to a nearby round figure such as the nearest 10 or 100, or to a number of significant figures — and then drop the rest. The single digit immediately after the cut-off decides the outcome: if it is 5 or more you round the last kept digit up, and if it is 4 or less you leave it as it is. This “round half up” rule is the one taught in school and used by most everyday calculators.
Three ways to round
Pick the method that matches the precision you need.
| Method | What you set | Example | Result |
|---|---|---|---|
| Decimal places | How many digits after the point | 3.14159 to 2 dp | 3.14 |
| Nearest unit | The unit to snap to (10, 100, 1000…) | 1234 to nearest 100 | 1200 |
| Significant figures | How many meaningful digits | 0.04567 to 3 sig figs | 0.0457 |
Worked example
Round 3.14159 to 2 decimal places:
- 1 Choose the precision. Here we want 2 decimal places, so the cut-off falls right after the second digit past the point: 3.14|159.
- 2 Find the deciding digit. The first digit being dropped is the one just after the cut-off — in 3.14159 that is the 1 in the thousandths place.
- 3 Apply the half-up rule. If the deciding digit is 5 or more, add 1 to the last kept digit; if it is 4 or less, leave the kept digits unchanged. Here 1 is below 5, so we round down.
- 4 Drop the rest. Remove every digit after the cut-off. 3.14159 rounded to 2 decimal places is 3.14.
Half-up, bankers’ rounding, and chained errors
What happens at exactly 5. The interesting case is a deciding digit of exactly 5 with nothing meaningful after it, such as 2.5 to a whole number. The common “round half up” rule always pushes it up, giving 3. An alternative, round half to even (also called bankers’ rounding), instead rounds to the nearest even digit — so 2.5 → 2 but 3.5 → 4. Spreading the ties evenly stops a long column of figures from drifting upward, which is why finance and many statistics packages prefer it. This calculator uses round half up.
Don’t round, then round again. Each rounding throws a little information away, and rounding an already-rounded value compounds the loss. Round 2.346 to two decimals and you get 2.35; round that to one decimal and you get 2.4 — but rounding the original 2.346 straight to one decimal gives 2.3. Always round once, from the most precise figure you have, to the precision you actually need.