Percentage Calculator - Six Percentage Tools in One
Six percentage calculators on one page: percent of a number, what percent one number is of another, increase and decrease, add or subtract a percentage, reverse percentages and percentage difference.
What is X% of Y?
X is what percent of Y?
Percentage increase or decrease
Add or subtract a percentage
Reverse percentage — X is P% of what number?
Percentage difference between two numbers
Formulas used
What is a Percentage Calculator?
A percentage is just a fraction with 100 as the denominator — but percentage questions come in several shapes, and the formula changes with the shape. Finding 15% of a number is a different operation from finding what percentage 45 is of 300, and both differ from working backwards to an original value. This page puts all six variants in front of you at once so you never have to work out which formula applies.
The Six Calculations Explained
- X% of Y — the basic case. (X ÷ 100) × Y. 15% of 1,200 is 180.
- X is what % of Y — turns two amounts into a share. (X ÷ Y) × 100. 45 out of 300 is 15%.
- Percentage increase or decrease — measures change against a starting value. ((New − Old) ÷ |Old|) × 100.
- Add or subtract a percentage — Y × (1 ± X ÷ 100). Adding 15% VAT to 2,000 gives 2,300.
- Reverse percentage — recovers the original number. (X ÷ P) × 100. If 90 is 30% of something, that something is 300.
- Percentage difference — compares two values symmetrically against their average, so neither is treated as the baseline.
Common Percentage Calculator Use Cases
Discounts
Work out a sale price, or the original price before the discount.
VAT & Tax
Add 15% to a net price or extract it from a gross total.
Exam Scores
Convert marks out of any total into a percentage.
Growth Rates
Measure month-on-month change in sales or traffic.
Tips & Commission
Calculate a tip, a commission or a bonus percentage.
Budget Shares
See what share of your income each expense takes.
The Percentage Mistake Almost Everyone Makes
Percentages do not cancel out. A 20% rise followed by a 20% fall does not return you to the start: 100 rises to 120, then a 20% fall from 120 is 24, leaving 96. The reason is that each percentage applies to a different base. The same logic explains why a 50% loss needs a 100% gain to recover, and why stacked discounts are always worth less than their sum.
Percentage Points vs Percentages
These are not the same thing, and conflating them is a common source of misleading statistics. If an interest rate moves from 4% to 5%, that is a rise of one percentage point but a 25% increase in the rate. Both statements are true; they answer different questions. Always check which one a headline is using.
How to Use This Calculator
- Find the card that matches the question you are asking.
- Type your numbers directly into the sentence.
- The answer updates instantly as you type — there is no button to press.
- Check the formula list at the bottom if you want to reproduce the maths by hand.
Who This Calculator Is For
- Students working through percentage problems
- Shoppers checking discounts and offers
- Small business owners pricing products
- Analysts calculating growth and change
- Teachers converting marks to percentages
- Anyone who wants the answer without remembering the formula
❓ Frequently Asked Questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For example, 15% of 1,200 is 0.15 × 1,200 = 180.
How do I work out what percent one number is of another?
Divide the part by the whole and multiply by 100. For example, 45 out of 300 is (45 ÷ 300) × 100 = 15%.
How do I calculate percentage increase?
Subtract the old value from the new value, divide by the old value, then multiply by 100. Going from 250 to 325 is a 30% increase.
How do I calculate percentage decrease?
Use the same formula — a negative result means a decrease. Going from 325 to 250 is a 23.08% decrease.
Why is a 20% rise then a 20% fall not back to the start?
Because each percentage applies to a different base. 100 rises to 120, but a 20% fall from 120 is 24, leaving 96 rather than 100.
What is a reverse percentage?
It finds the original number when you only know a part and its percentage. If 90 is 30% of a number, the original is (90 ÷ 30) × 100 = 300.
How do I find the price before a discount?
Divide the sale price by (1 − discount ÷ 100). A price of 240 after a 20% discount means the original was 240 ÷ 0.8 = 300.
What is the difference between percentage change and percentage difference?
Percentage change compares a new value against a specific starting value. Percentage difference compares two values against their average, so it has no direction.
How do I add a percentage to a number?
Multiply by (1 + percentage ÷ 100). Adding 15% VAT to 2,000 gives 2,000 × 1.15 = 2,300.
Is this percentage calculator free?
Yes. All six calculators are free, need no sign-up, and run entirely in your browser.