Percentage Calculator — % of, % Change, Discount & Marks
Four percentage calculations in one place: X% of a number, what percent X is of Y, percentage increase or decrease between two numbers, and marks or discount percentages.
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In short
X% of Y = X ÷ 100 × Y; X as a percent of Y = X ÷ Y × 100; percentage change = (new − old) ÷ old × 100; price after a discount = price × (1 − discount ÷ 100); marks percentage = obtained ÷ total × 100. A 20% fall then a 20% rise leaves you 4% down, and percentage points are not the same as percent.
Who this is for: Students, shoppers and business users who need a quick, correct percentage with the working shown.
The five percentage formulas
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | X ÷ 100 × Y | 15% of 2,400 = 360 |
| X is what % of Y? | X ÷ Y × 100 | 360 of 2,400 = 15% |
| % change from X to Y | (Y − X) ÷ |X| × 100 | 2,400 → 2,760 = +15% |
| Price after a discount | price × (1 − d ÷ 100) | 2,400 at 15% off = 2,040 |
| Marks percentage | obtained ÷ total × 100 | 880 of 1,100 = 80% |
Two traps: a 20% fall followed by a 20% rise does not get you back to the start (100 → 80 → 96), and percentage points are not percentages — a rate moving from 10% to 12% is a 2-point rise but a 20% increase.
Pakistani board grades (matric and intermediate) use 80%+ = A+, 70–79% = A, 60–69% = B, 50–59% = C, 40–49% = D, 33–39% = E; below 33% is a fail. Universities use the HEC 4.0 scale instead — see our CGPA calculator.
Assumptions
- Five modes with the formulas shown in the working line; percentage change divides by the absolute starting value.
- Marks mode maps to common Pakistani board grade bands (A+ 80%+ … E 33%).
- Results are rounded to 4 decimal places for display only.
Worked example
After discount: 2,400 × 0.85 = PKR 2,040. Adding 18% GST: 2,040 × 1.18 = PKR 2,407 — the tax almost exactly cancels the discount, because 0.85 × 1.18 = 1.003.
Frequently asked questions
How do I add a percentage to a number?
Multiply by (1 + percentage ÷ 100): adding 18% to 2,000 is 2,000 × 1.18 = 2,360. Use the discount mode with a negative percentage, or the VAT/GST calculators for tax specifically.
How do I calculate percentage increase in salary?
(new salary − old salary) ÷ old salary × 100. A rise from PKR 80,000 to 92,000 is 15%.
How do I work out a reverse percentage?
To find the original price before a 15% discount, divide by 0.85: 2,040 ÷ 0.85 = 2,400. The 'X is what % of Y' mode helps check it.
How are marks converted to percentage for matric?
Marks obtained ÷ total marks × 100 — 935 out of 1,100 is 85%. Boards print the percentage on the result card to two decimals.
What is 15% of 2,400?
360 — 15 ÷ 100 × 2,400.
What percentage is 880 out of 1,100?
80% — 880 ÷ 1,100 × 100, an A+ on the Pakistani board scale.
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