Calculator24 by Def24 Inc.

Calc24 puts a real calculator in your browser toolbar. Open it as a popup, or dock
it in the side panel and keep it beside your work while you browse.

Six modes, one calculator:

• Basic — the everyday keypad, with memory and a running result as you type.
• Scientific — trigonometry, logarithms, powers, roots, factorials, degrees or
radians.
• Notepad — work down a page of lines. Name a value and reuse it, refer to the
line above with "ans" or the running sum with "total", and edit any line to
recompute everything below it.
• Programmer — hex, decimal, octal and binary side by side, with AND/OR/XOR/NOT,
shifts and rotates, 8- to 64-bit words, and a bit grid you can click.
• Date — the days between two dates, or a date shifted by years, months and days.
• Converter — mix units in one expression: "5 ft + 3 in in cm", "2 GB / 15 Mbps",
"120 km / 2 h in mph". Currency too.

Everything else you would expect: multiple calculator tabs you can name and fork,
history and pinned results you can copy or reuse with one click, and six themes.

Your calculations stay on your device. There are no accounts, no tracking, and
the only network request the extension makes is for currency exchange rates —
and the converter still works without it, on rates bundled with the extension.

Open source calculator, also on the web at calc24.org.