Rounding Calculator
Round a number to set decimal places or the nearest unit, with floor and ceiling.
Round to nearest unit
- 1
Scale factor = 10^2
10^2 = 100 - 2
Multiply by scale factor
3.14159 × 100 = 314.159 - 3
Round to nearest integer
round(314.159) = 314 - 4
Divide by scale factor
314 ÷ 100 = 3.14
Formula
How this is calculated
You enter three things: the number to round, how many decimal places to keep, and an optional unit (1, 10, 100 or 1000) to round to the nearest multiple of. The decimal-place count is clamped to the range 0 to 15 because that is the limit of double-precision floating point; values outside it are pushed back inside before any maths happens.
For decimal rounding the value is scaled up by ten to the power of the chosen places, shifted by half a unit, truncated to an integer, then scaled back down. This is round-half-up: a digit exactly on the boundary, such as 2.5, always goes to the larger value (3). Floor takes the largest integer that is not greater than the number and ceiling takes the smallest integer that is not smaller, so they always move down and up regardless of the fraction. Rounding to a unit divides by that unit, rounds to the nearest whole number, then multiplies back.
Results are unitless and assume ordinary base-ten numbers. Because they rely on floating-point arithmetic, a few numbers with no exact binary form (like 1.005) can round in a way that looks surprising, and very large magnitudes may lose precision.
About this calculator
Rounding replaces a number with a nearby value that is simpler to read or store. Standard rounding goes to the nearest value, with halves rounding up. You can round to a number of decimal places or to the nearest unit such as 10, 100, or 1000.
This calculator also shows the floor (the largest integer not greater than the value) and the ceiling (the smallest integer not less than the value), which always round down and up respectively regardless of the fractional part.
Frequently asked questions
Floor always rounds down to the nearest integer, while standard rounding goes to the nearest integer, rounding 2.5 up to 3 but 2.4 down to 2.
Divide the number by 100, round to the nearest whole number, then multiply by 100. This calculator does it automatically when you pick the unit.
This tool uses round-half-up, so a value exactly halfway between two options rounds to the larger one (for example 2.5 becomes 3).
Also known as
TG we-Calculate Editorial Team. (2026). Rounding Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/rounding-calculator
TG we-Calculate Editorial Team. "Rounding Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/rounding-calculator.
TG we-Calculate Editorial Team, "Rounding Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/rounding-calculator
@misc{wecalculate_rounding_calculator, title = {Rounding Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/rounding-calculator}}, year = {2026}, note = {TG we-Calculate} }
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