Percentages show up everywhere: a 20% sale, a 15% tip, a 5% pay rise. Master three simple questions and you'll handle almost any of them — or just use the percentage calculator.
1. What is X% of a number?
Multiply the number by the percentage as a decimal. 20% of 50 is 50 × 0.20 = 10. This is the maths behind every discount and sales tax total.
2. X is what percent of Y?
Divide and multiply by 100. 30 out of 150 is 30 ÷ 150 × 100 = 20%. Handy for test scores, tips and "how much of my budget did I spend?"
3. Percentage change
Subtract, divide by the original, multiply by 100. Going from 80 to 100 is a 25% increase. This is the same idea behind investment growth and price rises.
Once you're comfortable, the tip calculator and discount calculator handle the everyday cases instantly.