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 · International · Modern
parsec
pcexact
- Record
- M272
- Definition quality
- Standardized
- Conversion mode
- multiplicative
- Calculator
- Fully calculable
Definition
Parsec: exactly (648,000/π) astronomical units; about 3.08567758149×10^16 m.
Reference value
One parsec is equal to 3.085678 × 10^+16 metres.
History & use
The name reflects the geometric parallax construction: a distance associated with one arcsecond of parallax.
Modern use
Core professional astronomy unit for stellar and galactic distances.
Did you know?
Because the AU is exact, the parsec's metre value follows exactly from π and the AU definition.
Sources & evidence
Source tier Tier A · confidence High
Related measurements
length · International · Modern
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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.