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What is covered
Eight categories: length, weight, temperature, area, volume, speed, time and digital storage. Conversion factors are the standard internationally defined values, and results run to nine decimal places — far more precision than everyday work needs, and considerably more than most of the measurements being converted actually have.
Notes on particular categories
Temperature
Temperature is the odd one out. Every other category converts by simple multiplication, because the units share a zero point. Temperature scales do not: 0 °C and 0 °F describe different physical states, so conversion needs both a multiplication and an offset. That is why doubling 10 °C does not double the Fahrenheit figure.
Volume
The gallons, quarts, pints, cups and fluid ounces here are US customary measures. Imperial units still used in the UK differ noticeably — an imperial pint is about a fifth larger than a US pint — which is the usual reason a recipe carried across the Atlantic goes wrong.
Digital storage
These use binary multiples, where one kilobyte is 1,024 bytes. Storage manufacturers advertise in decimal multiples, where a kilobyte is 1,000 bytes. The gap compounds at every step, which is why a drive sold as 1 TB shows up as roughly 931 GB once formatted.
Time
Months are treated as 30 days and years as 365 days, the standard simplification for rough durations. Where exact calendar dates matter — contract terms, notice periods, deadlines — use the date difference calculator instead, which counts real calendar days including leap years.
Two systems, one world
Most of the world uses the metric system, formalised as the International System of Units and built on a small set of base units related by powers of ten. The United States keeps customary units derived from imperial measures for everyday use, while its scientific and medical fields work in metric. The United Kingdom sits in between, mixing miles and pints with grams and litres in ordinary life.
The practical result is that anyone dealing with recipes, shipping, travel, equipment specifications or overseas suppliers converts constantly — and that errors carry real cost. The most expensive example on record remains the Mars Climate Orbiter, lost in 1999 after one team supplied thrust data in pound-seconds while another expected newton-seconds.
Frequently asked questions
How accurate are the results?
Conversion factors are the standard internationally defined values and results are shown to nine decimal places. Very large and very small results switch to scientific notation so nothing is silently rounded away.
Why do the storage numbers not match my hard drive?
This converter uses binary multiples, where a kilobyte is 1,024 bytes. Storage is marketed in decimal multiples, where a kilobyte is 1,000 bytes, which makes the advertised capacity look larger than what your operating system reports.
Are the gallons US or imperial?
US customary. An imperial gallon is roughly a fifth larger, so fuel figures and recipes from the UK will not match directly.
Can I convert currency here?
No. Exchange rates change by the minute and would need a live server feed, which this site does not use. Everything here rests on fixed physical relationships that never change.
Does it work without a connection?
Once the page has loaded, every conversion runs on your device.