Number Rounding Calculator: Decimals, Tens, Hundreds
Round any number to decimal places, tens, hundreds, thousands or other magnitudes with half-up, half-even, floor, ceiling or truncate.
Rounded
round(3.14159, 2) = 3.14
Quick reference: rounding 3.14159 with half-up
Round to
Result
4 decimals
3.1416
3 decimals
3.142
2 decimals
3.14
1 decimal
3.1
Whole number
3
Tens
0
Frequently asked questions
What is "round half up" and why is it the default?
Half-up is the rule taught in school and used in most everyday contexts: when the digit after the rounding place is exactly 5, round up. Example: 2.5 → 3, 2.45 → 2.5, 2.45000001 → 2.5. It is the standard for receipts, invoices and student work.
What is banker's rounding (half to even)?
Half-even rounds 0.5 toward the nearest even number: 2.5 → 2, 3.5 → 4, 4.5 → 4. Over many values the bias of always rounding up cancels out, so it is the IEEE 754 default and the choice for financial and statistical sums where systematic drift would distort totals. JavaScript's Math.round uses half-up; this calculator implements both methods explicitly.
How do I round to the nearest hundred or thousand?
Pick "Nearest 100" or "Nearest 1,000" from the rounding place dropdown — or click the preset chip. Internally the input is divided by the magnitude, rounded, then multiplied back: 1,234 with nearest 100 → divide by 100 (12.34) → round (12) → multiply (1,200). Useful for reporting figures, headlines, or when precision below a threshold is noise.
What is the difference between round, floor, ceiling and truncate?
Round picks the nearest value (half-up by default). Floor always goes toward negative infinity: floor(2.9) = 2, floor(−2.1) = −3. Ceiling always goes toward positive infinity: ceil(2.1) = 3, ceil(−2.9) = −2. Truncate simply drops digits and goes toward zero: trunc(2.9) = 2, trunc(−2.9) = −2. For positive numbers floor and truncate match; for negative they differ.
Why does 1.005 not round to 1.01?
Because 1.005 cannot be represented exactly in binary floating point — it is stored as 1.00499999…. Naïve rounding sees the 4 and rounds down. This calculator works on the input string before it becomes a float, so 1.005 with 2 decimals gives 1.01 as you would expect. The same problem in spreadsheets or naïve toFixed(2) often surprises people.
How do negative numbers round?
By absolute value with half-up: −2.5 rounds to −3 (i.e. away from zero). With half-even, −2.5 rounds to −2. Floor on −2.5 is −3 (toward minus infinity), ceiling is −2 (toward plus infinity), truncate is −2 (toward zero). Pick the method that matches the rule your project requires.
How many decimal places should a result keep?
As many as the least precise input. If you measured a length to 3 significant figures, the area calculated from it cannot be more precise than 3 figures either — extra digits are noise. For currency, follow the local convention: 2 decimals for USD, EUR, GBP; 0 for JPY, KRW, CLP, COP. Banks usually round in the bank's favour at the cent level.
All rounding happens in your browser using exact decimal logic, not floating-point.
Round any number to a chosen number of decimal places — tenths, hundredths, thousandths up to six — or to whole units, tens, hundreds, thousands and beyond. Pick the method that matches the rule your work requires: half-up (the school-book default), half to even (banker’s rounding, used by IEEE 754 and statistical software), half-down, ceiling, floor or simple truncate. The calculator works on the input as an exact decimal string, so 1.005 rounded to two decimals correctly returns 1.01 — not 1.00 as naive floating-point would give. Examples: 3.14159 → 3.14 at two decimals, 2.5 → 2 with banker’s rounding but 3 with standard, 1,234 → 1,200 nearest hundred, −2.5 → −3 half-up but −2 half-even. The result block shows the original value, the rounding rule applied, and the absolute change. A reference table covers the most frequent rounding places. Use the preset chips for one-tap rounding to two decimals, one decimal, whole number, tens, hundreds or thousands.