How to calculate percentages?

Question

I want to calculate what is $x percentage of a $total. $x could be 15%, 20%, etc, and $total could be 1000, 2000, etc. So I'd want the 15% of 1000, for example.

What is the formula for calculating this? (I know this isn't exactly a coding question but I'm coding this feature and need help!

Answer 1

Given X and Y, X% of Y is X * Y/100. If using integer arithmetic, make sure you do (X * Y)/100, not (X / 100) * Y.

15% of 1000 is (15*1000)/100, which is 150.

Answer 2

formulas:

percentage = partialAmount / totalAmount
totalAmount = partialAmount / percentage
partialAmount = percentage * totalAmount

note that percentage is normally a decimal number between 0 and 1

Answer 3

Don't know if I'm missing something here but if you just want the percentage of a number it's just multiply it by the percentage and divide by 100:

NewTotal = Total * Percentage / 100

IE:

NewTotal = 1000 * 15/100

or

NewTotal = 1000 * 0.15

Answer 4

(actual / available) * 100 = percent // start

actual / available = percent / 100

actual = (percent / 100) * available // finish

E.g. 15% of 1000

actual = (15 / 100) * 1000
actual = 0.15 * 1000
actual = 150

Answer 5

Though this particular question has been answered, you may find this site very helpful for basic algebra topics.

http://www.purplemath.com/modules/index.htm