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 · Astronomy / geodesy · Modern scientific reference
Earth radius
variant
- Record
- M279
- Definition quality
- Standardized
- Conversion mode
- variant selection
- Calculator
- Variant selection required
Definition
Earth radius is definition-dependent; the cited USGS/WGS84 implementation distinguishes equatorial, polar and authalic mean radii rather than one universal radius.
Reference value by variant
Earth radius covers several documented traditions, each with its own value. Choose a variant below to see a figure.
Modern use
Modern use is context-dependent and varies by region or measurement system.
Sources & evidence
Source tier — · confidence high
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.