Round decimals - to the nearest whole number
Theory
To round a decimal to the nearest whole number, look at the tenths digit: round up if it is \(5\) or more, down if it is less. Only the tenths digit matters — digits further right do not change the decision.
Rounding replaces a number with the nearest whole number, which is easier to work with.
Find the two whole numbers the decimal sits between and their halfway point. If the tenths digit is \(5\) or more, round up; if it is \(4\) or less, round down.
A tenths digit of exactly \(5\) means the number is halfway, and the rule is to round up.
Read only the tenths digit, then round.
| Decimal | Tenths digit | Rounds to |
|---|---|---|
| \(6.3\) | \(3\) (down) | \(6\) |
| \(4.5\) | \(5\) (up) | \(5\) |
| \(9.5\) | \(5\) (up) | \(10\) |
How to round to the nearest whole number
- Find the tenths digit of the decimal.
- Round up the whole number if the tenths digit is \(5\) or more.
- Keep the whole number the same if the tenths digit is \(4\) or less.
Tenths digit \(3 < 5\), so round down.
| \(6.3\) | \(=\) | \(6\) |
Tenths digit \(5\), so round up.
| \(4.5\) | \(=\) | \(5\) |
Rounding up moves into the next ten.
| \(9.5\) | \(=\) | \(10\) |
Tenths digit \(6 \geq 5\), so round up.
| \(19.60\) | \(=\) | \(20\) |
Common pitfalls
Frequently asked questions
Which digit do you look at?
The tenths digit, the first digit after the decimal point. If it is \(5\) or more, round up; if it is \(4\) or less, round down.
What happens with a decimal like 2.499?
The tenths digit is \(4\), so it rounds down to \(2\). Digits after the tenths never change the decision.
Which way does 4.5 round?
Exactly halfway rounds up, so \(4.5\) becomes \(5\).
Can rounding add a digit?
Yes. \(9.5\) rounds up to \(10\), which has an extra digit because it moves into the next ten.