Rounding Calculator

Written byOleh Soloninupdated 10 September 2026

Number

Decimal places

Method

Result

Result3
Error introduced0.5
To a whole number3
To tens0
To hundreds0

Standard, bankers, up, down and truncate

Rounds to any place by five different rules, including round-half-to-even, and reports the error the rounding introduced.

The school rule is simple: five or more goes up, less goes down. The problem shows up over a long column of figures, where every exact half tipping the same way biases the total upward.

Accounting and statistics therefore use bankers rounding, where halves go to the nearest even digit. 2.5 becomes 2 and 3.5 becomes 4, and across a large dataset the bias disappears.

What this calculator shows

The result under your chosen rule and the error it introduced
Values to the nearest whole number, ten and hundred for quick comparison
The difference standard and bankers rounding make on your figures

What to keep in mind

A negative number of places rounds to the left of the point: −2 means to the nearest hundred.
"Always up" and "always down" follow the number line rather than magnitude; truncation has its own mode.

FAQs

What is bankers rounding?

Halves go to the nearest even number. It removes the systematic upward bias when totalling many rounded values, which is why it is standard in financial reporting and in IEEE 754.

Why doesn't 0.1 + 0.2 equal 0.3?

Neither has an exact binary representation, so the sum lands on 0.30000000000000004. Rounding to a sensible number of places is the usual fix.

How many decimals should money use?

Two, and only on the final result. Rounding intermediate values accumulates error that becomes visible in long calculations.

How does truncation differ from rounding down?

Not at all for positive numbers. For negatives it does: −2.7 rounds down to −3 but truncates to −2.

Worked example

An exact half

Input: 2.5 to a whole number

Output: Standard 3, bankers 2

Note: The two rules only differ on exact halves. 2.6 rounds to 3 either way, and 2.4 rounds to 2 either way.

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Result

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