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Rounding Calculator
A rounding calculator rounds any number to the decimal place you choose, to the nearest 5, 0.5, 0.25, 10, 100, or 1000, or to a number of significant figures — using round half up, the rule you learned in school, or banker's rounding (round half to even), which you can pick instead. Enter a number, pick how to round it, and the answer appears instantly — perfect for homework, prices, measurements, and quick estimates.
| Original number | |
| Rounded number | |
| Difference (rounded − original) |
How it works
Rounding replaces a number with a nearby number that is shorter and easier to use. You choose a place value — the digit you want to keep as the last one — and then look at the digit right after it. If that next digit is 5 or more, you round the kept digit up by one; if it is 4 or less, you leave the kept digit as it is and drop everything after it. That simple look-at-the-next-digit rule is the whole method.
This calculator uses round half up by default, the rule taught in most classrooms: when the dropped part is exactly half, the number rounds up. So 2.5 rounds to 3, 7.5 rounds to 8, and 1.25 rounded to one decimal place becomes 1.3. Some computer systems use a different rule called banker's rounding, which rounds a trailing 5 to the nearest even number — 2.5 becomes 2 and 3.5 becomes 4 — because it avoids a small upward bias when many numbers are rounded. You can switch methods with the dropdown above; the two rules only ever differ on exact halves.
Nearest 10 / 100 / 1000: divide by 10, 100, or 1000, round to a whole number, then multiply back
Nearest 5 / 0.5 / 0.25: divide by the step, round to a whole number, then multiply back
Significant figures: round x to n digits starting from the first non-zero digit
Rule: next digit 5 or more → round up; 4 or less → round down. Banker's rounding sends an exact half to the nearest even digit.
Rounding to a whole number or a number of decimal places is the most common case, and it is how money works: a bill of $12.3456 becomes $12.35, because prices keep two decimal places. Rounding to the nearest 10, 100, or 1000 is for estimates — a crowd of 8,473 people is "about 8,500", a distance of 1,240 miles is "about 1,200 miles", and a budget of $47,800 is "about $48,000". The bigger the rounding step, the rougher the estimate and the easier the number is to remember.
Negative numbers follow the same rule, with "up" meaning away from zero: −2.5 rounds to −3 under round half up. One warning: rounding in the middle of a long calculation can change the final answer, so it is best to keep full precision while you work and round only at the end, when you present the result. Rounding a price at each step of a receipt, for example, can leave the total off by a few cents.
Worked example
A student in Miami, Florida, is working with pi, 3.14159, and needs it rounded to two decimal places for a geometry problem.
Step 1 — find the digit to keep: two decimal places means keeping the 4 in 3.14, so the kept part is 3.14. Step 2 — look at the next digit: the digit after the 4 is 1, which is less than 5, so the kept digit stays the same. The answer is 3.14.
For a second check, take 2.5 rounded to zero decimal places. The digit to keep is the 2, the next digit is 5, and round half up says a trailing 5 rounds up — so 2.5 becomes 3. Enter 3.14159 with 2 decimal places in the calculator above and you get 3.14; switch the number to 2.5 with 0 decimal places and you get 3.
FAQ
What does round half up mean?
Round half up means that when the digit you are dropping is exactly 5, you round up to the next value. So 2.5 rounds to 3, 3.5 rounds to 4, and 1.25 rounded to one decimal place becomes 1.3. This is the rounding rule taught in most schools and used in everyday life.
What is the difference between round half up and banker's rounding?
Banker's rounding, also called round half to even, rounds a trailing 5 to the nearest even number, so 2.5 becomes 2 and 3.5 becomes 4. Round half up always rounds a trailing 5 upward, so 2.5 becomes 3. This calculator lets you choose either method, with round half up as the default.
What are significant figures?
Significant figures count the meaningful digits of a number, starting from the first non-zero digit. Rounding 12,345 to 3 significant figures gives 12,300, and rounding 0.004567 to 2 significant figures gives 0.0046. They are used in science and engineering to show how precise a measurement really is.
How do you round to the nearest 10 or 100?
Look at the digit just below the place you are rounding to. To round 47 to the nearest 10, look at the 7 in the ones place: since 7 is 5 or more, round up to 50. To round 432 to the nearest 100, look at the 3 in the tens place: since 3 is less than 5, round down to 400.
Why do we round numbers?
Rounding makes long numbers short and easy to use. A price of $3.14159 is rounded to $3.14 because money only uses two decimal places, and a crowd of 8,473 people is reported as about 8,500 because the exact count matters less than the size. Rounding trades a little accuracy for numbers people can remember and work with.