Round to the nearest tenth?
Type a number. The round to the nearest tenth calculator keeps one decimal place and tells you which digit decided the answer.
- Rounded number
- 18.4
18.379 rounded to the nearest tenth is 18.4.
- Why
- The hundredths digit is 7, which is 5 or more, so the tenths digit goes up by 1.
- Number
- 18.379
Rounded number: 18.4. 18.379 rounded to the nearest tenth is 18.4.
How to calculate
Rounds any number to the nearest tenth (one decimal place) in exact decimals, and says which digit decides.
Example with the default inputs (Number to round 18.379): 18.379 rounded to the nearest tenth is 18.4.
Method: Look at the hundredths digit: 5 or more rounds the size of the number up to the next tenth; less than 5 keeps the tenths digit. Every digit to the right is dropped.
- The number is taken as the decimal it is written as, so an exact halfway value is a true tie.
- Halves round away from zero (round half up on the size of the number): a negative number rounds like its size, with the minus sign kept.
Worked examples
Each example is checked against the calculator on every build.
- Number to round 18.379 gives Rounded number 18.4, Why The hundredths digit is 7, which is 5 or more, so the tenths digit goes up by 1..Source: OpenStax, Prealgebra 2e, section 5.1 Decimals (round 18.379 to the nearest tenth: 18.4), https://openstax.org/books/prealgebra-2e/pages/5-1-decimals (retrieved 2026-11-01)
- Number to round 3.14159 gives Rounded number 3.1, Why The hundredths digit is 4, which is less than 5, so the tenths digit stays..Source: OpenStax, Prealgebra 2e, section 5.1 Decimals (round 18.379 to the nearest tenth: 18.4), https://openstax.org/books/prealgebra-2e/pages/5-1-decimals (retrieved 2026-11-01)
- Number to round 1.45 gives Rounded number 1.5.Source: OpenStax, Prealgebra 2e, section 5.1 Decimals (round 18.379 to the nearest tenth: 18.4), https://openstax.org/books/prealgebra-2e/pages/5-1-decimals (retrieved 2026-11-01)
- Number to round -2.25 gives Rounded number −2.3.Source: OpenStax, Prealgebra 2e, section 5.1 Decimals (round 18.379 to the nearest tenth: 18.4), https://openstax.org/books/prealgebra-2e/pages/5-1-decimals (retrieved 2026-11-01)
- Number to round 9.96 gives Rounded number 10.0.Source: OpenStax, Prealgebra 2e, section 5.1 Decimals (round 18.379 to the nearest tenth: 18.4), https://openstax.org/books/prealgebra-2e/pages/5-1-decimals (retrieved 2026-11-01)
- Number to round -0.04 gives Rounded number 0.0.Source: OpenStax, Prealgebra 2e, section 5.1 Decimals (round 18.379 to the nearest tenth: 18.4), https://openstax.org/books/prealgebra-2e/pages/5-1-decimals (retrieved 2026-11-01)
How it works
This is the rounding calculator with its place fixed at tenths. Take the number as the decimal it is written as, and let n be its size without any minus sign.
- Rounded number = ⌊10n + ½⌋ ÷ 10, with the minus sign put back. A number that rounds to 0 shows as 0, with no minus sign.
- Why says which way the hundredths digit, ⌊100n⌋ mod 10, went. The exact text is either "The hundredths digit is d, which is 5 or more, so the tenths digit goes up by 1." or "The hundredths digit is d, which is less than 5, so the tenths digit stays."
- Number repeats the input with up to 20 decimals and thousands commas. A number too small to show in 20 decimals is shown in its plain form (1e-21), with a true minus sign when negative (−1e-21).
Rules
- The arithmetic is exact: the input is read as its shortest decimal, not as a binary float, so 1.45 is a true tie and rounds to 1.5.
- Every number has an answer, including 0 and very large numbers.
- The rounded number shows with exactly one decimal place.
Worked examples by hand
18.379. The hundredths digit is 7, so the 3 goes up by 1: 18.4.
3.14159. The hundredths digit is 4, so the 1 stays: 3.1.
1.45. The hundredths digit is 5, so the 4 goes up by 1: 1.5.
−2.25. The size 2.25 has a 5 in the hundredths place, so it rounds to 2.3: −2.3.
9.96. The hundredths digit is 6, and the 9 in the tenths place carries: 10.0.
−0.04. The hundredths digit is 4, so the tenths digit stays 0: 0.0.
Other questions people ask
How do you round to the nearest tenth?
Look at the hundredths digit, the second digit after the decimal point. If it is 5 or more, add 1 to the tenths digit. If it is less than 5, keep the tenths digit. Then drop every digit after the tenths place. 18.379 has a 7 in the hundredths place, so it rounds to 18.4.
What is the tenths place?
It is the first digit after the decimal point. In 18.379 the tenths digit is 3, the hundredths digit is 7, and the thousandths digit is 9.
Does the third decimal digit matter?
No. Only the hundredths digit decides. 2.349 rounds to 2.3, because its hundredths digit is 4. The 9 after it does not push the 4 up first.
What is 9.96 rounded to the nearest tenth?
10.0. The hundredths digit is 6, so the 9 in the tenths place goes up by 1. That carries into the ones place, and 9 becomes 10.
How do negative numbers round?
Round the size of the number and keep the minus sign. −2.25 rounds to −2.3, the same way 2.25 rounds to 2.3. So a half rounds away from zero.
Why does the answer show a zero at the end, such as 10.0?
The zero shows that the number is correct to one decimal place. 10.0 and 10 have the same value.