Everyday Math

How to Calculate Percentage — Simple Guide with Real Examples

June 20264 min readMyCalcKit Editorial

Percentages appear everywhere — discounts, tax, interest rates, exam scores, statistics. Here are the three calculations you actually need to know.

Type 1: What Is X% of Y?

The most common percentage question. Formula: Result = (X ÷ 100) × Y

Examples:

What is 20% of £150? → (20 ÷ 100) × 150 = £30
What is 8.5% of $45,000? → (8.5 ÷ 100) × 45,000 = $3,825
What is 15% tip on $67? → (15 ÷ 100) × 67 = $10.05

Type 2: What Percentage Is X of Y?

When you want to express one number as a percentage of another. Formula: Result = (X ÷ Y) × 100

Examples:

What percentage is 45 of 180? → (45 ÷ 180) × 100 = 25%
You scored 68 out of 80. What percentage? → (68 ÷ 80) × 100 = 85%
£35,000 salary, £7,000 pension. What percentage? → (7,000 ÷ 35,000) × 100 = 20%

Type 3: Percentage Change

Used for price changes, salary increases, investment returns. Formula: Result = ((New - Old) ÷ Old) × 100

Examples:

Price was £80, now £92. What is the increase? → ((92 - 80) ÷ 80) × 100 = +15%
Salary was $55,000, now $62,000. → ((62,000 - 55,000) ÷ 55,000) × 100 = +12.7%
Investment fell from £10,000 to £8,500. → ((8,500 - 10,000) ÷ 10,000) × 100 = -15%

Quick Mental Math Tricks

To calculate...	Do this...
10% of any number	Move decimal point one place left (10% of 450 = 45)
5% of any number	Find 10% then halve it (5% of 450 = 22.5)
20% of any number	Find 10% and double it
25% of any number	Divide by 4
15% tip	Find 10%, add half of that

Percentage vs Percentage Points

Important distinction: if an interest rate rises from 4% to 5%, it has risen by 1 percentage point — but by 25% (relative change). Politicians and media often use these interchangeably, which is misleading.

Calculate any percentage instantly — percentage of a number, percentage change, and percentage difference.

Percentage Calculator