Percentage Calculator
Calculate percent values.
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The percentage calculations people actually need
Percentage means "per hundred", and most confusion comes from mixing up several distinct questions that all use the word. What is 15 per cent of 240? That is multiplication. 36 is what percentage of 240? That is division. What is the percentage change from 240 to 276? That is the difference over the original value.
Two traps recur. A percentage increase followed by an equal-looking decrease does not return you to the start: 100 raised by 20 per cent is 120, and 120 reduced by 20 per cent is 96. And percentage points are not percentages — an interest rate moving from 4 to 6 per cent is a rise of two percentage points but a 50 per cent increase, and news reports frequently conflate the two. Knowing which question you are asking is most of the work.
Why we built this tool
Percentages run through daily life: discounts and sale prices, VAT and sales tax, tips, interest, commission, exam marks, and any comparison of a change over time.
None of it is sensitive in isolation, but the figures often are — a salary, a loan balance, a business margin. Ours computes in your browser with no request made, which keeps those numbers on your machine, returns the answer instantly, and works offline. It is the same principle behind every tool here: a calculation the browser can perform has no business being sent to a server, and building it locally removes both the privacy question and the latency.
Tips and common mistakes
- A 20 per cent rise followed by a 20 per cent fall does not return you to the starting figure.
- Percentage points and percentages are different things, and news reports frequently confuse them.
- Percentage change divides by the original value, not the new one.
- Sanity-check every result against a rough mental estimate before acting on it.
Open Percentage Calculator with a link
Percentage Calculator can be handed its input by the link that opens it, so the page arrives with the work already done. This is meant for assistants and scripts: if a chatbot, an editor extension, or a command-line agent already holds your content, it can build a link instead of asking you to copy and paste into a box.
The payload rides in the fragment — the part of a URL after the #. Browsers never send the fragment to a server, so anything handed over this way stays on your device exactly as a dropped file would. A link that uses the query string instead is rewritten into the fragment by the page before any analytics or ad script can read the address.
Prefix any field with gz — #gza= — to pass it as gzip-compressed base64url, which fits roughly five to ten times more into the same link. Links stay reliable up to about 8,000 characters; past that, chat apps and address bars start truncating them, and the page says so rather than loading half a document.
One exception to the privacy rule: ?url= tells the page to download the input from an address. That request goes from your browser straight to that server — not through ours — but it does leave your device, and it only works if the server allows cross-origin requests.
#a=— the first side to compare#b=— the second side to compare
Example: https://mygadgets.ink/tools/percentage-calculator/#a=...&b=...
Quick start: using Percentage Calculator
- Choose the type of calculation you need.
- Enter your values in the fields provided.
- Read the result and sanity-check it against a rough mental estimate.
- For changes over time, make sure you are dividing by the original value.
- Watch the distinction between a percentage change and a change in percentage points.
For more involved arithmetic, use the Scientific Calculator.