How to Calculate Percentages — Complete Guide with Examples
Three types of percentage calculations explained with formulas and real examples. Use our free calculator for instant answers.
Three formulas:
1. X% of a number: Number × (X ÷ 100)
2. What % is A of B: (A ÷ B) × 100
3. % change: ((New − Old) ÷ Old) × 100
1. X% of a number: Number × (X ÷ 100)
2. What % is A of B: (A ÷ B) × 100
3. % change: ((New − Old) ÷ Old) × 100
→ Use our free Percentage Calculator for instant answers
Type 1: Finding X% of a number
| Question | Working | Answer |
|---|---|---|
| 10% of 200 | 200 × 0.10 | 20 |
| 15% of 80 | 80 × 0.15 | 12 |
| 25% of $350 | 350 × 0.25 | $87.50 |
Type 2: What percentage is A of B?
| Question | Working | Answer |
|---|---|---|
| What % is 45 of 200? | (45 ÷ 200) × 100 | 22.5% |
| What % is 30 of 75? | (30 ÷ 75) × 100 | 40% |
Type 3: Percentage increase or decrease
| Scenario | Working | Result |
|---|---|---|
| Price rises $80 → $100 | ((100−80) ÷ 80) × 100 | +25% |
| Price drops $120 → $90 | ((90−120) ÷ 120) × 100 | −25% |
Quick percentage shortcuts
- 10% — divide by 10
- 5% — find 10% then halve it
- 20% — divide by 5
- 25% — divide by 4
- 50% — divide by 2
How do I add VAT (20%) to a price?
Multiply by 1.20. Example: £100 + 20% VAT = £100 × 1.20 = £120. To remove VAT from a gross price, divide by 1.20.
How do I calculate a percentage tip?
For 15%: find 10% (divide by 10), add half of that (5%). Example: 15% tip on $45 = $4.50 + $2.25 = $6.75. For 20%: divide by 5.