How do I calculate the percentage of a number?

Question

I would like to calculate, in PHP, the percentage of a number. For example:

$percentage = 50;
$totalWidth = 350;

For this example, 50% of 350 = 175

How can I do that?

score 195 · Accepted Answer · edited Aug 26 '20 at 21:47

195

$percentage = 50;
$totalWidth = 350;

$new_width = ($percentage / 100) * $totalWidth;

edited Aug 26 '20 at 21:47

Joundill

answered Apr 18 '12 at 00:23

pogeybait

5

No one cares about $totalWidth = 0... Why? – Georgy Liparteliani Sep 20 '14 at 14:06
3

@GeorgyLiparteliani because any percentage of zero is zero. The variable $totalWidth isn't the dividend, is a multiplicator. – jloria Oct 14 '14 at 16:50
12

50% of 350 = 175 I would do it that way, it's more logical for me: `($totalWidth*$percentage)/100` it is the same, but I like it more. – vinsa Dec 28 '14 at 23:58
its helpful, thanks and +1 for accurate answer :) – Aditya P Bhatt Jan 05 '15 at 19:54
There's no need for parentheses. Multiplication and division have the same priority and therefore `$new_width = $percentage / 100 * $totalWidth;` it's the same – Eugen Zaharia Dec 07 '16 at 11:08
1

Simple and concise. I prefer the parenthesis, whether they are needed by the rules of precedence or not. It makes order clear, and readable. – Marlon van der Linde Jun 22 '17 at 14:25

score 26 · Answer 2 · answered Apr 18 '12 at 00:17

26

Divide $percentage by 100 and multiply to $totalWidth. Simple maths.

answered Apr 18 '12 at 00:17

hkf

in case the type is an integer it is better if you multiply first, then divide by 100. Example when dividing first: int answer = 50/100 = 0.5 (int rounds 0.5 to 1); answer*width = 1*350 = 350. D'oh. – Ozzy Apr 18 '12 at 00:37
2

@Ozzy Types don't matter here. If a calculation results in a fraction, the result will automatically be a float and won't be rounded. – deceze Apr 18 '12 at 01:12

2 Answers2