How to Calculate Percentage

1. What is X% of Y?

To find what X percent of Y is, multiply Y by X and divide by 100.

Formula: (X ÷ 100) × Y

Example: What is 20% of 150?

(20 ÷ 100) × 150 = 0.2 × 150 = 30

2. X is what percent of Y?

To find what percentage X is of Y, divide X by Y and multiply by 100.

Formula: (X ÷ Y) × 100

Example: 30 is what percent of 150?

(30 ÷ 150) × 100 = 0.2 × 100 = 20%

3. Percentage Increase

When a value goes from an old value to a new value, the percentage increase is:

Formula: ((New − Old) ÷ Old) × 100

Example: Price increased from 50 to 75.

((75 − 50) ÷ 50) × 100 = (25 ÷ 50) × 100 = 50% increase

4. Percentage Decrease

When a value decreases from old to new:

Formula: ((Old − New) ÷ Old) × 100

Example: Price dropped from 80 to 60.

((80 − 60) ÷ 80) × 100 = (20 ÷ 80) × 100 = 25% decrease

5. Add or Subtract a Percentage

Add X% to a value: Value + (Value × X ÷ 100)

Subtract X% from a value: Value − (Value × X ÷ 100)

Example (add 15% to 200): 200 + (200 × 15 ÷ 100) = 200 + 30 = 230

Quick reference

• What is X% of Y? → (X/100) × Y
• X is what % of Y? → (X/Y) × 100
• Increase → ((new − old)/old) × 100
• Decrease → ((old − new)/old) × 100