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 · Ancient Greek · Classical/Hellenistic
plethron
variant
- Record
- M131
- Definition quality
- Variant-dependent
- Conversion mode
- variant selection
- Calculator
- Variant selection required
Definition
1 plethron = 100 selected Greek feet
Reference value by variant
plethron covers several documented traditions, each with its own value. Choose a variant below to see a figure.
History & use
Used for length and land contexts.
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.