Unit Converters
Converters, each on its own page, each running entirely in your browser.
Currency Converter
Convert foreign currencies (USD, EUR, GBP, INR, JPY, CAD, AUD, and more) with real-time conversion rates.
Open converter →PX to REM Converter
Convert CSS pixels to REM or EM against any root font size, with a lookup table of the common values.
Open converter →Aspect Ratio Calculator
Reduce any pixel dimension to its simplest ratio, with the decimal form and the standard ratio it matches.
Open converter →Byte Converter
Convert between bytes, KB, MB, GB, and TB using binary multiples — the figures your operating system reports.
Open converter →Conversion rules explained
These look like one kind of tool and are not. The pixel converter depends on a setting that can change underneath you — the root font size — which is the entire reason rem exists. The aspect ratio calculator is pure arithmetic with no configuration at all. The byte converter depends on which of two competing definitions of a kilobyte you accept.
Only the middle one has a single correct answer. The other two are worth understanding rather than just using.
Frequently asked questions
Why should CSS use rem instead of px?
Because a reader who raises their browser’s default text size expects the page to follow. Lengths in px ignore that setting; lengths in rem scale with it. It is one of the cheapest accessibility improvements available.
Is a kilobyte 1000 or 1024 bytes?
Both are in use. Software generally counts in binary multiples of 1024, storage manufacturers in decimal multiples of 1000. That difference is why a drive sold as 1 TB shows as about 931 GB once formatted. The byte converter here uses 1024.
Why does 1366×768 not reduce to 16:9?
Because it is not exactly 16:9. It reduces to 683:384, since 1366 is not exactly sixteen ninths of 768. The decimal figures — 1.779 against 1.778 — show how close it is, which is why it is marketed as widescreen.
Is anything I enter sent to a server?
No. All converters run in your browser and nothing is transmitted or stored.