FIELD NOTE 01 / MEASUREMENT
A practical unit conversion reference
A converted number is only useful when the source unit, destination unit and precision are clear. This page summarizes the conventions used by the Measureline converter.
Length and mass use scale factors
For units with a fixed relationship, the converter maps both units to a shared base and then maps to the target. For example, 1 inch is exactly 0.0254 metre, and 1 international foot is exactly 0.3048 metre. The NIST Guide to the SI documents customary-unit conversions and explains that rounding should match the precision of the original measurement.
Exact unit definitions do not make a measured input exact. If someone measured a board as 12 inches to the nearest inch, a long decimal in millimetres would not add real measurement precision. The tool shows up to eight significant digits so the arithmetic is visible without implying every input was measured that accurately.
Temperature is different
Celsius, Fahrenheit and kelvin do not share a zero point. Conversion therefore needs an offset as well as a scale: °F = (°C × 9/5) + 32; K = °C + 273.15. A temperature interval is different from an absolute temperature: a change of 1 °C equals a change of 1 K, while the same interval is 1.8 °F.
Use the right data-size prefix
Decimal prefixes advance by powers of 1,000: 1 MB = 1,000 kB. Binary prefixes advance by powers of 1,024: 1 MiB = 1,024 KiB. The distinction matters when comparing a file manager, a disk specification or a network rate. A byte is also different from a bit; 8 bits make 1 byte.
| Unit | Multiplier in bytes | Prefix family |
|---|---|---|
| kB | 1,000 | Decimal |
| MB | 1,000,000 | Decimal |
| KiB | 1,024 | Binary |
| MiB | 1,048,576 | Binary |
When not to trust a generic conversion
Check the source convention when a label is ambiguous. “Ton,” “gallon,” “cup,” “ounce” and “mile” can refer to different units in different regions or contexts. This tool uses the international avoirdupois pound and the U.S. customary fluid ounce is not included. Engineering tolerances, medication dosages and regulated specifications need the governing standard and a suitably precise source measurement.
Try the converter
Open the unit converter and select Length, Mass, Temperature or Data size. The units in each family are kept separate to prevent mixing dimensions.