What it does
Percentages turn up everywhere: sale prices, price rises, pay changes, tax, commission and profit. This page has six small calculators in tabs, each with an example already filled in, so you can see what to type. It answers instantly and shows the sum in words, so you can check it makes sense.
Everything runs in your browser and nothing is sent anywhere. When you are planning what to spend, the budget planner is a good next step.
How to use it
- Pick the tab that matches your question.
- Type your numbers. The answer updates as you type.
- Read the sentence under the answer to be sure you asked the right question.
What each tab does
- X% of Y: finds a share of an amount, such as 15% of 80.
- X is what % of Y: turns two numbers into a percent, such as a score of 12 out of 80.
- % change: from an old value to a new one, shown as an increase or a decrease.
- Add or remove %: adds a percent (tax, tip), takes one off (a discount), or works back to the original price when the amount already includes the percent.
- Stacked discounts: two or three discounts one after another. They are not added: 30% off then 10% off is 37% off, not 40%, because the second discount applies to the smaller price.
- Markup and margin: markup is profit as a share of what it cost you; margin is profit as a share of what you sell it for.
Worked example
A shop buys a jacket for 80 and sells it for 100. The profit is 20. That is a markup of 25% (20 out of 80) and a margin of 20% (20 out of 100). Later the jacket gets 30% off, then a further 10% off at the till: the true total discount is 37%, so the 100 jacket costs 63.
FAQs
Why is 30% then 10% not 40%? Each discount is taken from the price left after the one before it. The calculator multiplies what remains: 0.70 x 0.90 = 0.63, so 37% off.
How do I find the price before tax? Use “Add or remove %”, choose “Amount already includes it”, and enter the tax percent.
What is the difference between markup and margin? Same profit, different base. A 25% markup is only a 20% margin, so do not mix them up when pricing.
Where the numbers come from
- Standard percentage formulas. Nothing region-specific; fibub's own working.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-10.