0.4 as a fraction
0.4 is 4 tenths, so write it as 4/10 and simplify to 2/5.
The answer
0.4 = 2/5
How to write 0.4 as a fraction
Put the digits in a place value chart. The place of the last digit tells you the bottom of the fraction.
| Ones | Tenths |
|---|---|
| 0 | 4 |
The last digit is in the tenths column, so 0.4 is 4 tenths: 4/10.
Simplify by dividing the top and bottom by the same number. In one go, divide by the highest common factor (the biggest whole number that divides both exactly), 2: 4/10 = 2/5.
2 and 5 share no factor except 1, so 2/5 is the simplest form.
As a percentage, 0.4 = 40%: multiply by 100, which moves each digit two places to the left.
To check, divide back: see 2/5 as a decimal and 2/5 as a percentage.
See 2/5
Shade 2/5 on a fraction wall
This wall shows selected denominators: halves, thirds, quarters, fifths, sixths, eighths and tenths. Other fractions on this site may not have a row here. The wall opens with 2/5 shaded in the fifths row. Look straight down: the shading ends in exactly the same place in 4/10, so it is equal to 2/5. Tap other pieces to try more fractions.
A fraction wall from halves to tenths, opening on 2/5.
More decimals as fractions
Questions parents ask
What is 0.4 as a fraction in its simplest form?
0.4 = 4/10 = 2/5. Divide the top and bottom of 4/10 by 2 to get 2/5.
How do you write 0.4 as a fraction?
The last digit of 0.4 is in the tenths column, so write the digits over 10: 4/10. Then simplify if you can.
What is 0.4 as a percentage?
0.4 = 40%. Multiply by 100: the digits move two places to the left.
Continue your maths practice
Explore the diagnostic for another way to practise.