The decimal form of 4/5 is .8, which can also be written as 0.8 or 0.80. Fractions can be converted into decimals using a calculator or by doing the math manually.
To find the decimal form of 4/5 on a calculator, type in the number four, hit the division symbol, press the number five, and then hit the equal sign. To do the math manually, multiply the bottom number by another number to make it a multiple of 10. The number can be multiplied by two to make it 10. Then take the two and multiply it by the top number, which is four. This results in a fraction of 8 over 10. Next, take the top number, which is eight, and move the decimal at the end of it left, according to how many zeros are in the bottom number. Since 10 has one zero, move the decimal left one time, providing .8 as the solution.