Calculator
A plain calculator with big buttons. It does × and ÷ before + and −, handles brackets, and keeps a history you can tap to reuse.
Keyboard works too: digits, + − * /, %, ( ), Enter for =, Backspace, Esc to clear.
Runs on your device. Nothing is uploaded. Your history is kept only in this browser until you clear it.
History
How % works here
| 200 + 10% = 220 | Adds 10% of 200 (a tip, a VAT or a price rise). |
| 200 − 10% = 180 | Takes 10% of 200 off (a discount). |
| 50 × 10% = 5 | 10% of 50. |
| 50 ÷ 10% = 500 | 50 divided by 0.1. |
| 10% = 0.1 | On its own, % divides by 100. |
This is how most shop and phone calculators behave. Spreadsheets read 200 + 10% as 200.1, so check which one you need.
Good to know
Brackets first, then × and ÷, then + and −, left to right. So 2 + 3 × 4 is 14, not 20. Cheap calculators that work left to right give 20.
M+ adds the number on the screen to memory, M− takes it away, MR puts the memory into your sum and MC clears it. Handy for adding up a few totals.
Computers store numbers in binary, so 0.1 + 0.2 is really 0.30000000000000004. Results here are rounded to 12 significant digits, so you see 0.3.
Sources: the order of operations is the standard mathematical convention. Binary rounding: IEEE 754 double-precision numbers, which browsers use for JavaScript numbers (ECMAScript specification). The percent key follows the common behaviour of basic calculators described in the table above; spreadsheet programs treat % as "divide by 100" everywhere. The sum is worked out by this page's own small parser, never by running your text as code.