What is Percentage Calculator?
A percentage calculator answers the questions a single percent-off tool does not cover. It works in both directions, so it can tell you that 15% of 240 is 36 and that 36 is 15% of 240. It measures growth and decline between two values, rebuilds a total from a known part, and keeps a separate money mode for tax, tips, markups, budget shares and target margins. Every answer is printed as an arithmetic line so it can be checked by hand.
Best for
- Checking a test or survey score
- Working out tax, tips and retail markups
- Splitting a budget into shares or percentages
- Pricing a product to a target margin
Privacy
Values live in the page while it is open and are gone when you close it. Nothing is stored, no history is kept between visits, and no figure is sent anywhere. Presets, the proportion bar and the formula lines are all produced in the browser as you type.
Quick tips
- Percentage change divides by the absolute value of the starting number. A figure moving from -50 to -25 is therefore reported as +50% and not as -50%, because the number itself went up. Keep the sign of your starting value in mind when it is a negative balance.
- When the part is larger than the whole, the answer is above 100% and the bar changes to an overflow marker instead of running past the edge. That is a real result, not a fault.
- Profit Margin works backwards from a target: it divides the cost by the share you want to keep, so 60 of cost at a 30% margin sells for 85.71. If 30% means 30% on top of the cost, use Tax/Markup/Tip instead, which gives 78.
How to use this tool
- Open the tab that matches your question: the first for percentage maths, the second for money and budget percentages.
- Fill in the two numbers, or use a preset for the rates that come up most, such as 20% or a standard tax rate.
- Read the result and the formula printed under it. Every card carries a copy button for that single answer.
- In the money tab, pick the operation that matches the job and set the currency for display. Copy Breakdown puts the itemized figures on the clipboard as plain text.
Common questions
How do I calculate what percentage one number is of another?
Divide the part by the whole and multiply by 100. For 36 out of 240 that is (36 ÷ 240) × 100 = 15%. Type 36 and 240 into the second card and the same figure appears with a bar showing how much of the whole it fills.
How do I work out a percentage increase or decrease?
Take the difference between the two values, divide by the starting value, and multiply by 100. From 240 to 264 that is (264 - 240) ÷ 240 × 100 = +10%, and the sign shows which way it moved. A starting value of zero has no percentage, so that card returns a message instead of a number.
What is reverse percentage, and when is it the wrong tool?
Reverse percentage rebuilds a whole from a part that is a stated share of it: 30 is 20% of 150, so (30 ÷ 20) × 100 = 150. It is not the same as undoing a discount, because a price 20% off is 80% of the original and needs dividing by 0.8 rather than by 20. For that case use the Discount Calculator.
How do I price a product to hit a profit margin?
Divide the cost by the share of the price you want to keep. At a 30% margin on 60 of cost the selling price is 60 ÷ (1 - 0.30) = 85.71, which leaves 25.71 of profit. The two measures are easy to confuse: margin is taken from the selling price, markup from the cost, so 60 marked up 30% is 78.
How do I add a percentage to a price, or take one off?
Multiply the amount by the rate, then add or subtract the result. Tax/Markup/Tip adds the percentage to the amount you type, Discount takes it off, and both show the portion separately from the new total; presets cover 8%, 20% and an 18% tip. The share mode answers a different question, how much of a budget a percentage represents, and leaves the remainder on screen. Yen is shown without decimals.
Are the numbers I type sent to a server?
No. Each calculation runs in the tab and the values are not stored or carried into a later visit. The currency selector picks the symbol and the number of decimals, so choosing euros changes how a figure is written rather than what it is worth, and no exchange rate is fetched.