Percentage Calculator
Find a percentage of any number, and see the value after increasing or decreasing it by that percentage.
The percentage calculator answers the most common percentage questions in one place: what is X% of a number, and what does that number become if you add or subtract that percentage. It is handy for discounts, marks, tips, interest and everyday maths.
How to use the calculator
- Enter the percentage you are working with.
- Enter the value it applies to.
- Read the result instantly: the percentage amount, plus the increased and decreased values.
- Use the increase/decrease figures for markups, price rises, weight changes and more.
How it is calculated
Increase: Y × (1 + X ÷ 100) · Decrease: Y × (1 − X ÷ 100)
Worked example
15% of 200
15% of 200 = 30
200 increased by 15% = 230 and decreased by 15% = 170.
Who should use this calculator
- Students checking marks, grade boundaries and percentage scores.
- Shoppers and small business owners working out discounts, margins and price changes.
- Anyone checking a bank, loan or tax figure expressed as a percentage of an amount.
- People converting a fraction into a share of a total for a report or a presentation.
Common mistakes to avoid
- Adding percentages of different bases. A 10% rise followed by a 10% fall does not return you to the starting point, because the second calculation uses the new, larger figure.
- Confusing percentage points with percentages. Moving from 10% to 12% is a rise of two percentage points, but a 20% increase in relative terms. Both are correct descriptions of different things.
- Reversing a percentage the wrong way. If a price after tax is ₹1,180 including 18%, the base is ₹1,180 ÷ 1.18, not ₹1,180 minus 18%.
- Mixing up "X% of Y" with "X is what % of Y". The first gives an amount, the second gives a proportion. Choosing the wrong one produces a plausible but wrong answer.
- Rounding too early. Rounding a percentage to a whole number halfway through a chain of calculations can shift the final figure noticeably.
Percentage rises and falls are not symmetrical
Start at 100, add 20% and you have 120. Take 20% off that and you are back at 96 — four below where you began. The reason is that the second percentage applies to 120, not to 100, so the fall is 24 rather than 20.
This asymmetry matters more than it looks. A share that falls 50% needs to rise 100% just to break even. A salary that is cut 10% needs an 11.1% raise to be restored. And in investing, a portfolio that drops 30% requires a 43% gain to recover. Whenever a percentage change moves in both directions, calculate each step on the value at that moment rather than on the original.
Percentage terms explained
- Base value
- The number the percentage is applied to. Getting the base wrong is the source of most percentage errors.
- Percentage change
- The increase or decrease expressed as a share of the original value: (new − old) ÷ old × 100.
- Percentage points
- The simple arithmetic difference between two percentages, without dividing by the base.
- Reverse percentage
- Finding the original amount when you know the final figure and the rate — dividing rather than multiplying.
- Compound percentage
- Applying a percentage repeatedly to the changing value, as happens with interest, inflation and stacked discounts.
- Fraction to percentage
- Multiply the fraction by 100. Three-quarters becomes 75%, and 0.4 becomes 40%.
Everyday uses worth remembering
Percentages turn up constantly once you start noticing them. Marks: 78 out of 120 is 65%. Interest: 8% a year on ₹50,000 is ₹4,000. Tips and taxes: 18% of a bill is the amount divided by 100 and multiplied by 18, or simply multiplied by 0.18. Discounts: 30% off means paying 70%, so multiply by 0.7 rather than subtracting and hoping. And any time a figure rises and falls by the same percentage, expect to end up slightly below where you started — the base changed in between.
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage and divide by 100. For example, 15% of 200 is 200 × 15 ÷ 100 = 30.
How do I add a percentage to a number?
Multiply the number by (1 + percentage ÷ 100). To add 15% to 200, calculate 200 × 1.15 = 230.
What is the difference between percentage and percentage points?
A percentage is a share of a whole, while a percentage point measures the change between two percentages. Going from 10% to 12% is a rise of 2 percentage points, but a 20% relative increase.