Eight categories, sixty-odd units, one conversion at a time. Answers update as you type.
Every category except temperature works through a base unit — meters, kilograms, liters, seconds and so on. Your value is multiplied by the source unit's factor to reach the base, then divided by the target's, which keeps the conversion table small and the arithmetic exact for the ratios that are defined exactly. Temperature needs a different approach because its scales have different zero points, so values pass through Celsius rather than a multiplication.
Results keep six significant figures. That matters at the small end: a milligram expressed in kilograms is 0.000001, and a converter that rounds to four decimal places would simply report zero.
US liquid measure, along with quarts, pints, cups, tablespoons and teaspoons. A UK imperial gallon is about 20% larger, so recipes and fuel figures from British sources need care.
A kilobyte is 1,000 bytes; a kibibyte is 1,024. Storage manufacturers use the decimal version and operating systems often use the binary one, which is why a 1 TB drive shows as roughly 931 GB. Both are available above.
So the arithmetic is predictable. Real calendar years vary with leap days, so use the day converter and count them if precision matters.
The imperial-to-metric factors are the internationally defined exact values — an inch is exactly 25.4 mm and a pound exactly 0.45359237 kg. Displayed answers are rounded for readability, not the maths behind them.