Every percentage problem reduces to one of seven formulas. Master these and you'll never need to Google 'how to calculate percentage' again.
The one formula that powers everything
Every percentage calculation derives from: Percentage = (Part ÷ Whole) × 100. Rearrange this equation and you can answer any percentage question.
The 7 essential formulas
- What % is A of B? → (A ÷ B) × 100
- What is X% of B? → (X ÷ 100) × B
- A is X% of what? → A ÷ (X ÷ 100)
- % increase from A to B → ((B − A) ÷ A) × 100
- % decrease from A to B → ((A − B) ÷ A) × 100
- Add X% to A → A × (1 + X ÷ 100)
- Remove X% from A (reverse percentage) → A ÷ (1 + X ÷ 100)
Real-world examples
Sale price: a jacket marked $80, 25% off → 80 × (1 − 0.25) = $60.
Tip: a $48 dinner, 18% tip → 48 × 0.18 = $8.64.
Grade: 47 out of 60 on an exam → (47 ÷ 60) × 100 = 78.3%.
Reverse VAT: gross price £120 at 20% VAT → 120 ÷ 1.20 = £100 net.
Salary raise: $52,000 raised by 6% → 52,000 × 1.06 = $55,120.
The 3 mistakes everyone makes
- Adding then subtracting the same %. A $100 product up 20% then down 20% is $96, not $100.
- Confusing percentage points with percent. Going from 5% to 8% is +3 percentage points, but a +60% relative increase.
- Using the new value as the base for percentage change. Always divide by the original.
Skip the math — use the free tools
SnapFetch's Percentage Calculator handles all 7 formulas with one click. For shopping, use the Discount Calculator. For US tax, the Sales Tax Calculator. For UK/EU, the VAT Calculator.
All four are free, no signup, mobile-friendly.
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