UNIT CONVERSION REFERENCE
Use 220 verified direct converters, then check the unit definitions, exact relationships, rounding guidance and common mistakes behind the result.
Length describes one-dimensional distance. SI length scales by powers of ten; the international inch, foot, yard and mile have exact metre definitions.
Reference: 1 km = 1,000 m · 1 m = 100 cm = 1,000 mm · 1 in = 25.4 mm exactly
Common mistake: Keep linear length separate from area and volume, where conversion factors must be squared or cubed.
Mass measures the amount of matter. This family uses the SI kilogram and international avoirdupois definitions for pounds and ounces.
Reference: 1 kg = 1,000 g · 1 lb = 0.45359237 kg exactly · 1 stone = 14 lb
Common mistake: Do not substitute fluid ounces for mass ounces, or pounds-force for pounds of mass.
Volume describes three-dimensional capacity. Metric litres coexist with US customary and UK imperial liquid measures.
Reference: 1 L = 1,000 mL · 1 US gal = 3.785411784 L · 1 imperial gal = 4.54609 L
Common mistake: Always identify whether a gallon, cup or fluid ounce uses a US, imperial or metric convention.
Area measures two-dimensional surface. A length factor must be squared when converting an area.
Reference: 1 ha = 10,000 m² · 1 km² = 1,000,000 m² · 1 acre = 4,046.8564224 m²
Common mistake: A kilometre-to-metre factor of 1,000 becomes 1,000,000 for square kilometres to square metres.
Temperature scales have different zero points, so conversions require an offset as well as multiplication.
Reference: °F = °C × 9/5 + 32 · K = °C + 273.15
Common mistake: Kelvin has no degree symbol, and a temperature difference does not use the same offset as an absolute reading.
Speed combines distance and time. Road-speed conversion here uses the international statute mile and the kilometre.
Reference: 1 mph = 1.609344 km/h exactly
Common mistake: Average trip speed includes slow sections and stops; it should not be treated as a speed-limit recommendation.
Digital storage may use decimal prefixes (1 GB = 1,000 MB) or binary prefixes (1 GiB = 1,024 MiB).
Reference: 1 GB = 1,000 MB · 1 GiB = 1,024 MiB
Common mistake: Check whether software reports decimal GB or binary GiB before comparing a displayed capacity.
Open the digital storage converter →Length describes one-dimensional distance. SI length scales by powers of ten; the international inch, foot, yard and mile have exact metre definitions.
Mass measures the amount of matter. This family uses the SI kilogram and international avoirdupois definitions for pounds and ounces.
Volume describes three-dimensional capacity. Metric litres coexist with US customary and UK imperial liquid measures.
Area measures two-dimensional surface. A length factor must be squared when converting an area.
Temperature scales have different zero points, so conversions require an offset as well as multiplication.
Speed combines distance and time. Road-speed conversion here uses the international statute mile and the kilometre.