Not every conversion is a multiplier
Length, mass, area, volume and speed usually convert through a base unit. Temperature is different because Celsius and Fahrenheit use an offset. Digital storage is also special because providers may use decimal units such as GB or binary units such as GiB.
Common mistakes
- Converting square or cubic units as if they were linear units.
- Mixing US gallons with imperial gallons.
- Using Fahrenheit/Celsius as a simple multiplier.
- Confusing MB with MiB or Mbps with MB/s.
Exact conversion constants worth knowing
Several everyday metric-imperial conversions are exact by definition: 1 inch = 25.4 mm, 1 foot = 0.3048 m and 1 mile = 1,609.344 m. A US liquid gallon is 3.785411784 liters, while an imperial gallon is 4.54609 liters. That gallon distinction is why US MPG and imperial MPG are not interchangeable.
For calculator UX, unit labels are clearer when they include the system when ambiguity is common: US fl oz versus imperial fl oz, short ton versus metric tonne, and nautical mile versus statute mile. Temperature conversions are clearer when they show the formula because Celsius, Fahrenheit and kelvin do not share the same zero point.
Use the calculators
FAQ
Are imperial and US customary units the same?
Not always. Some names overlap, but volumes such as gallons can differ.
Why do area conversions look larger?
Area units are squared. A foot-to-meter conversion is linear, but square feet to square meters converts the two-dimensional measure.
Should I use GB or GiB?
Use the unit used by the provider or device specification. GB is decimal; GiB is binary.
References
- NIST: SI units, accessed 2026-05-16.
- NIST SP 1038 conversion factors, accessed 2026-05-16.
Last reviewed: 2026-05-16.