Format and unit converters

Eight converters for values that mean the same thing written another way. A timestamp of 1700000000 in a log is a specific date in your time zone; the color #ff5a1f is also rgb(255 90 31) and an oklch you can tweak; a 755 permission is rwxr-xr-x. Type into any field and the others update straight away, so they work just as well in both directions.

Some of them answer questions that come up a lot: why a 1 TB drive shows up as 931 GB (SI versus binary units), what 18 px is in rem with a 16 px base, or how much contrast a color has against white under WCAG. The currency converter uses the European Central Bank’s reference rates and does the maths in your browser, even offline.

All 8 tools

Unix timestamp converterLive Unix clock and conversion of timestamps in seconds or milliseconds to ISO 8601, UTC, local and relative time in any time zone, and back.
Color converterConvert colors between HEX, RGB, HSL and OKLCH with every field editable and in sync, and check their WCAG contrast against white and black.
Number base converterConvert numbers between binary, octal, decimal, hexadecimal and any base from 2 to 36, with no size limit and optional digit grouping.
Unit converterConvert length, mass, temperature, volume, area, speed and data, and see the value in every unit at once, each one with its own copy button.
Currency converterConvert between euros, dollars, pounds and 27 other currencies with ECB reference rates. The amount is computed in your browser and it works offline.
PX to REM converterConvert pixels to rem and em and back, with your own base font size. Includes ready-to-copy CSS and a table of common sizes.
Chmod calculatorConvert Unix permissions from octal (755) to symbolic (rwxr-xr-x) and back, tick boxes and copy the chmod command ready for the terminal.
File size converterType a size like 1.5 GB or 750 MiB and see it in SI and binary units, in bytes and in bits. Find out why a 1 TB drive shows 931 GB.