Percentage of a number: `p% of N = (p/100) * N`
Example formula: `25% of 80 = (25/100) * 80`
Convert percentage to decimal: `p% = p/100`
If you know the result and want the original number: `N = (result * 100) / p`
If you know the result and want the percentage: `p = (result * 100) / N`
If you need the percentage increase from A to B: `((B – A) / A) * 100`
If you need the percentage decrease from A to B: `((A – B) / A) * 100`