Utilities
Every percentage question, answered
Calculate percentages of numbers, percentage change, and increases or decreases, with the working shown.
For the best results: Choose the question shape first, "X% of Y" and "X is what % of Y" are different sums. The working line shows the formula so you can sanity-check it.
Computed entirely in your browser. Nothing you enter is uploaded, logged, or stored.
What is Percentage Calculator?
Percentage Calculator is a free online utility that answers every common percentage question (X% of Y, what percent X is of Y, and percentage change) with the working shown. The math runs right in the page, so the numbers you enter stay on your device and are never sent anywhere. There is no account step, no limit on how many times you calculate, and it keeps working offline.
- ✦Runs entirely in your browser. Nothing you enter is ever uploaded
- ✦No account, no sign-up, and no data leaves your device
- ✦Works offline once the page has loaded
See it in action
Two quick checks: what is 15% of 200, and what is the change from 80 to 100?
What you type
Mode "X% of Y" with 15 and 200; then mode "% change" with 80 and 100
What you get
15% of 200 = 30, and 80 to 100 is a rise of 25%, each with its working shown (200 × 15⁄100; (100 − 80) ÷ 80 × 100), verified in testing.
Tip: The working line is deliberate: seeing the formula stops the classic mix-up between percentage change and percentage points. The increase and decrease modes handle "what is X increased by Y%" without rearranging anything.
Use cases
What people use it for
Work out the actual dollars a 35 per cent discount saves before you reach the checkout
Turn a 62 out of 80 test result into the percentage an application form wants
Measure month-on-month revenue change without misreading a drop and a recovery as breaking even
Who uses Percentage Calculator?
Shoppers on a budget
compare discounts and unit prices quickly enough to decide at the shelf, not at home afterwards
High school students
check percentage homework against fully worked steps instead of copying an unexplained answer
Small retailers
set markups and markdowns knowing exactly what each does to the margin on every sale
How it works
- 1Vary step 1 by tool shape using the existing FORM_TOOL_IDS set in app/(public)/[category]/[tool]/page.tsx. Form tools get "Set the options for what you need." and text tools get "Paste your text into the box." Where a tool's config makes it easy, name its own inputs instead. Steps 2 and 3 stay shared as they are.
- 2Your browser computes the result instantly. Nothing is uploaded anywhere.
- 3Copy the output; the tool keeps working even offline.
Tips for the best results
- To undo a discount, divide by one minus the rate; never add the percentage back on
- Remember that x per cent of y equals y per cent of x, so 16 per cent of 25 is just 25 per cent of 16
- Say whether a change is percentage points or per cent whenever you report rates
- For stacked changes, multiply the factors: two 10 per cent rises give 21 per cent, not 20
- Sanity-check the sign of any percentage change before quoting it
FAQ
Frequently asked questions
Why does a 50 per cent fall not cancel a 50 per cent rise?
Each percentage is taken of a different base, and the asymmetry trips up even experienced people. Start at 100, fall 50 per cent to 50, then rise 50 per cent and you reach only 75. Recovering from a fall requires a larger percentage gain than the fall itself: a 20 per cent drop needs a 25 per cent rise, and a 50 per cent drop needs 100 per cent.
What is the difference between percentage points and per cent?
An interest rate moving from 4 to 6 per cent has risen two percentage points, but as a relative change it has grown 50 per cent. News reports blur the two constantly, and the gap between the readings can be enormous. Points describe the absolute distance between two percentages; per cent describes the relative change, and precise writing states which one it means.
How do I work out what percentage one number is of another?
Divide the part by the whole and multiply by 100, so 45 out of 180 gives 45 divided by 180, which is 0.25, or 25 per cent. The calculator performs exactly this and displays each substitution, which makes it easy to sanity-check: the part should be a quarter of the whole, and a quarter is indeed 25 per cent.
What does showing the working actually give me?
Every answer arrives with the formula and your numbers substituted into it, rather than a bare result. That lets you verify the calculation, reuse the method in a spreadsheet or exam, and catch input mistakes, because a typo tends to produce working that visibly reads wrong. A bare number gives you no way to notice any of that.
Is anything I calculate here visible to anyone else?
The arithmetic runs wholly within the page you are viewing, so salary negotiations, profit margins and exam marks are figures only you ever see. No request carries them anywhere, no record accumulates, and the calculator remains fully usable with networking disabled. Since no infrastructure sits behind it, there is also nothing to ration and no daily allowance.
How do you calculate percentage increase between two numbers?
Subtract the old value from the new, divide by the old value, then multiply by 100. Going from 80 to 92 gives 12 divided by 80, which is a 15 per cent increase. Keep the sign: a negative result is a decrease, and the base is always the earlier figure.
What is 20 per cent of 150?
Thirty. The quickest route is to find 10 per cent by shifting the decimal point, giving 15, then double it. This two-step habit handles most everyday percentages: 5 per cent is half of the 10 per cent figure, and 15 per cent is the two added together.
How do you reverse a percentage to find the original price?
Divide the discounted price by one minus the rate, rather than adding the percentage back on. An item at 80 dollars after 20 per cent off was originally 80 divided by 0.8, which is 100 dollars. Adding 20 per cent to 80 gives 96, wrong because the base changed.
Are there any usage limits?
None. Everything is generated locally in your browser, so there is no server cost, no metering, and no daily cap, use it as many times as you like, completely free.
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