Percentage Calculator — Work Out Any Percentage Free
Four calculators in one: percentage of a number, change, and reverse percentages.
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Works out the original figure before a percentage was added — handy for removing VAT or sales tax from a total.
Most percentage questions are one of four shapes, and this calculator handles all of them. Pick the tab that matches your question, type the numbers, and the answer updates as you go — there is no submit button.
How to use Percentage Calculator
- Pick your question type from the four tabs above.
- Enter your two numbers. The result recalculates on every keystroke.
- Read the explanation underneath the answer — it restates the whole calculation so you can check it is the sum you meant to do.
The four calculations
What is X% of Y?
Multiply the number by the percentage over 100. 15% of 200 → 0.15 × 200 = 30. This is the one you want for tips, discounts and commission.
X is what percent of Y?
Divide the part by the whole, then multiply by 100. 30 out of 200 → (30 ÷ 200) × 100 = 15%. Use it for scores, completion rates and market share.
Percentage increase or decrease
Subtract the old value from the new, divide by the old, multiply by 100. From 120 to 150 → ((150 − 120) ÷ 120) × 100 = 25% increase. This is the one for price changes, growth rates and salary rises.
Reverse percentage
Divide the final amount by 1 plus the percentage over 100. £230 including 15% tax → 230 ÷ 1.15 = £200 before tax. Use it to strip VAT or sales tax out of a total.
A common mistake worth knowing
A percentage increase followed by the same percentage decrease does not return you to where you started. £100 up 20% is £120; £120 down 20% is £96, not £100. The two percentages are calculated from different starting figures — which is exactly why a "50% off, then 20% off" sale is not 70% off.
Frequently asked questions
How do I calculate a percentage increase?
Subtract the original value from the new one, divide the result by the original, and multiply by 100. Going from 120 to 150: (150 − 120) ÷ 120 × 100 = 25%. The "% increase / decrease" tab does this for you.
How do I remove VAT or sales tax from a total?
Use the reverse percentage tab. Divide the gross amount by 1 plus the tax rate over 100. £230 including 15% tax gives 230 ÷ 1.15 = £200 before tax, and £30 of tax.
Why is a 20% rise then a 20% fall not back to the start?
Because the two percentages apply to different base numbers. The rise is 20% of the original; the fall is 20% of the larger amount, so it removes more. 100 → 120 → 96.
What is the difference between percentage points and percent?
If a rate moves from 5% to 7%, that is a rise of 2 percentage points, but a 40% increase. News reports often blur the two, and it changes the meaning substantially.