Editorial & conversion methodology
How we pick which units to include, how we compute, and what the limits are.
Unit selection
Every unit in unitbox comes from one of two sources: (1) the SI (International System of Units) and its defined prefixes, or (2) widely-used non-SI units that appear in daily life (US/UK gallons, nautical miles, BTU, etc.). We deliberately exclude obscure historical units that no one converts anymore.
Conversion factors
Length, mass, area, volume, speed, time, data, energy, pressure, angle — linear scaling, factor taken from NIST and BIPM. Temperature is affine (with offset) because of the zero-point shift. Fuel-economy is reciprocal — the smaller the L/100km number, the more efficient.
Precision
Default 6 significant figures. The "decimal/binary" data-prefix split (KB = 1000 bytes, KiB = 1024 bytes) follows IEC 80000-13. The US vs UK gallon difference is preserved.
Editorial policy
Articles are written for clarity over jargon. Each conversion page is generated from the same data table used by the live converter — no copy-pasted factor lists that can drift out of sync.
Updates
The site is open source. Every change is visible in the public commit log at github.com/longmao/unitbox.
Frequently Asked Questions
Where do your conversion factors come from?
NIST Special Publication 811 (SI factors), BIPM SI Brochure, and IEC 80000-13 for data prefixes. Each unit page links to its category reference.
How do you handle KB vs KiB (decimal vs binary)?
We use KB = 1000 bytes (decimal) and KiB = 1024 bytes (binary) per IEC 80000-13. We never silently round-trip between the two.
Why are temperatures affine (not linear)?
Because 0 °C is not the same point as 0 °F or 0 K. We apply the offset (0 °C = 273.15 K, 0 °C = 32 °F) before scaling.
Why is fuel-economy shown as "reciprocal"?
L/100km and MPG-US measure efficiency in opposite directions — smaller L/100km = better, larger MPG = better. We invert one before computing.