length · International · Modern
SI base unit of length. Its definition fixes the speed of light in vacuum at exactly 299,792,458 m/s, with the second defined from the caesium-133 hyperfine frequency.
Converter
length · U.S. surveying legacy · Retired 2022; historical/legacy data
survey foot (U.S., historical)
exact
- Record
- M593
- Definition quality
- Historically documented
- Conversion mode
- multiplicative
- Calculator
- Fully calculable
Definition
1 U.S. survey foot = 1200/3937 m ≈ 0.3048006096 m
Reference value
One survey foot (U.S., historical) is exactly 0.3048006096 metres.
History & use
NIST retired the U.S. survey foot after 2022; the international foot (0.3048 m exactly) is now the uniform U.S. foot basis.
Modern use
Modern use is context-dependent and varies by region or measurement system.
Sources & evidence
Related measurements
length · International · Modern
1 km = 1000 m by the SI prefix kilo-.
length · International · Modern
1 cm = 0.01 m by the SI prefix centi-.
length · International · Modern
1 mm = 0.001 m by the SI prefix milli-.
inch
inlength · UK / US · Modern / historical
1 international inch = exactly 0.0254 m.
foot
ftlength · UK / US · Modern / historical
1 international foot = exactly 0.3048 m.
yard
ydlength · UK / US · Modern / historical
1 international yard = exactly 0.9144 m.
mile
milength · UK / US · Modern / historical
1 international mile = exactly 1609.344 m = 1760 yd.