Every percentage formula you might need, in one printable reference. Plus conversion tables for fractions, decimals, and the special percentages worth memorizing.
| Want to find | Formula | Example |
|---|---|---|
| P% of X | X × P ÷ 100 | 15% of 80 = 12 |
| What % is Y of X | Y ÷ X × 100 | 12/80 = 15% |
| Y is P% of what | Y × 100 ÷ P | 12 = 15% of 80 |
| X increased by P% | X × (1 + P ÷ 100) | 80 + 15% = 92 |
| X decreased by P% | X × (1 − P ÷ 100) | 80 − 15% = 68 |
| % change from A to B | (B − A) ÷ A × 100 | 80 → 100 = +25% |
| % difference between A, B | |A − B| ÷ ((A+B)/2) × 100 | 40 vs 60 → 40% |
| P% discount on X | X × (1 − P ÷ 100) | $80 at 25% off = $60 |
| Markup → sell price | cost × (1 + markup ÷ 100) | cost $40, +50% = $60 |
| Margin from cost & sell | (sell − cost) ÷ sell × 100 | $40 cost, $60 sell → 33.3% |
| From | To | How | Example |
|---|---|---|---|
| Percent | Decimal | Divide by 100 | 15% → 0.15 |
| Percent | Fraction | P/100, simplify | 25% → 25/100 = 1/4 |
| Decimal | Percent | Multiply by 100 | 0.42 → 42% |
| Fraction | Percent | Divide top by bottom, × 100 | 3/4 → 75% |
| Percent | Decimal | Fraction |
|---|---|---|
| 1% | 0.01 | 1/100 |
| 5% | 0.05 | 1/20 |
| 10% | 0.1 | 1/10 |
| 12.5% | 0.125 | 1/8 |
| 20% | 0.2 | 1/5 |
| 25% | 0.25 | 1/4 |
| 33.3% | 0.333… | 1/3 |
| 50% | 0.5 | 1/2 |
| 66.7% | 0.667… | 2/3 |
| 75% | 0.75 | 3/4 |
| 100% | 1.0 | 1/1 |
| 200% | 2.0 | 2/1 |
They divide that same profit by different bases: markup divides by cost, margin divides by sell price. The sell price is always larger than the cost (when profitable), so margin is always lower than markup for the same dollar profit.
10%. It's a one-step calculation (move the decimal) and it's the building block for many others (5% is half, 20% is double, 15% is 10%+5%, etc.).
Divide the numerator by the denominator and multiply by 100. For 5/8: 5 ÷ 8 = 0.625; × 100 = 62.5%. With practice, you'll memorize common ones: 1/8 = 12.5%, 1/4 = 25%, 3/8 = 37.5%.