Round decimals - to 1 decimal place
Theory
To round a decimal to 1 decimal place, look at the hundredths digit: round the tenths up if it is \(5\) or more, down if it is less. Write the answer with exactly one digit after the point, so \(4.0\), not \(4\).
Rounding to 1 decimal place keeps one digit after the point — the tenths.
Look at the next digit, the hundredths. If it is \(5\) or more, round the tenths up; otherwise keep it.
The answer must show exactly one decimal place, so write \(4.0\), not \(4\).
Read the hundredths digit, then round the tenths.
| Decimal | Hundredths digit | Rounds to |
|---|---|---|
| \(6.34\) | \(4\) (down) | \(6.3\) |
| \(6.38\) | \(8\) (up) | \(6.4\) |
| \(0.96\) | \(6\) (up) | \(1.0\) |
How to round to 1 decimal place
- Find the hundredths digit, just after the tenths.
- Round the tenths up if the hundredths digit is \(5\) or more.
- Write the answer with one digit after the point.
Hundredths digit \(4 < 5\), so round down.
| \(6.34\) | \(=\) | \(6.3\) |
Hundredths digit \(8 \geq 5\), so round up.
| \(6.38\) | \(=\) | \(6.4\) |
The tenths digit \(9\) rounds up and carries.
| \(0.96\) | \(=\) | \(1.0\) |
Hundredths digit \(5\), so round up.
| \(8.25\) | \(=\) | \(8.3\text{ cm}\) |
Common pitfalls
Frequently asked questions
Which digit decides the rounding?
The hundredths digit, the second digit after the point. If it is \(5\) or more, the tenths rounds up.
Why write 4.0 instead of 4?
Rounding to one decimal place means the answer must show one digit after the point, so \(4.0\) shows the level of rounding.
What if the tenths is a 9?
Rounding a \(9\) up carries into the ones. \(0.96\) rounds to \(1.0\).
Do digits after the hundredths matter?
No. Only the hundredths digit decides. In \(1.449\) the hundredths digit is \(4\), so it rounds to \(1.4\).