Percentage calculator
What is X% of Y, what percent X is of Y, the percentage change between two numbers, and a price after a discount, with the method shown.
Pick the question, fill in the two numbers, press Calculate.
The five questions
| Question | Formula | Example |
|---|---|---|
| X% of Y | Y × X ÷ 100 | 18% of 2,500 = 450 |
| X is what % of Y | X ÷ Y × 100 | 432 out of 500 = 86.4% |
| Change from X to Y | (Y − X) ÷ X × 100 | 80 to 92 = +15% |
| Price after X% discount on Y | Y × (1 − X ÷ 100) | 15% off 2,499 = 2,124.15 |
| Original before X% was added to reach Y | Y ÷ (1 + X ÷ 100) | 1,180 with 18% GST in it = 1,000 |
Worked examples
Marks: 432 out of 500 is 432 ÷ 500 = 0.864, which is 86.4%. Shopping: a Rs 2,499 kurta at 15% off costs 2,499 × 0.85 = Rs 2,124.15, so the shop takes off Rs 374.85. Salary: a raise from Rs 80,000 to Rs 92,000 is an increase of 12,000 on 80,000, which is 15%. A fall from 92,000 back to 80,000 is a decrease of 12,000 on 92,000, which is 13.04%: the same rupee change is a different percentage each way, because the base changed.
Percent and percentage points
If an interest rate goes from 8% to 10%, it has risen by 2 percentage points and by 25 percent (2 is a quarter of 8). News reports mix the two. When someone says a figure "rose 5%", check whether they mean five points on a percentage or five percent of the old value; on a tax rate or an exam pass rate the difference is large.
Reversing a percentage
The one that catches people out is working backwards. A bill of Rs 1,180 that includes 18% GST did not start at 1,180 minus 18% (that gives 967.60). The tax was 18% of the original, so the original is 1,180 ÷ 1.18 = Rs 1,000 and the tax was Rs 180. The same applies to a "20% off" price when you want to know what the tag said: divide by 0.80, do not add 20%.
Rounding
The calculator shows up to two decimals. Money is rounded to the paisa; marks percentages are usually shown to one or two decimals as the board or university requires. Round only at the end, not in the middle of a chain of steps.