What you can convert here
Alongside the height converter, fuel economy and shoe size, this category holds converters generated from official tables for eleven quantities: length, mass, temperature, speed, volume, area, time, energy, pressure, angle and digital data. Each one converts between every unit of its quantity at once.
The three conversion traps
1. Units that share a name and differ in value. The US gallon holds 3,785 ml and the British Imperial gallon 4,546 ml — 20% larger. The same applies to pints, fluid ounces and tons (short, long and metric). When converting, always check which system the number came from.
2. Temperature is not proportional. Length, mass and volume are factor conversions: multiply and you are done. Temperature has a zero offset: 68 °F is not twice 34 °F, and the conversion requires adding or subtracting before multiplying. That is why "a 10-degree change" has to state which scale.
3. Area and volume do not scale like length. If 1 foot is 12 inches, 1 square foot is 144 square inches and 1 cubic foot is 1,728 cubic inches. Converting area with the linear factor is the error that produces answers off by orders of magnitude while the arithmetic looks perfectly reasonable.
Where the factors come from
Conversions use International System (SI) factors, with exact values fixed by international agreement — the inch has been exactly 25.4 mm since 1959, and the pound exactly 0.45359237 kg. Where a unit is culturally ambiguous, the page states which variant it applies.
Frequently asked questions
How many decimal places does the result show? Enough for the conversion to be reversible without perceptible loss. For practical use, round only at the end: converting, rounding and converting back accumulates error.
Is a kilogram weight or mass? Mass. Weight is a force, measured in newtons. The confusion is harmless day to day because Earth's gravity is essentially constant — but it is why your mass would be identical on the Moon and your weight one sixth.
Why is 1 kg not exactly 2.2 lb? Because the real factor is 2.20462. The 2.2 is a mental approximation with a 0.2% error — irrelevant for a suitcase, relevant for a recipe or a dosage.
MB or MiB? Two conventions coexist: drive manufacturers use MB as 1,000,000 bytes, while operating systems often display MiB (1,048,576 bytes) and label it MB. That is why a 1 TB drive "shows up" as roughly 931 GB — nothing is missing, the ruler changed.