Full name: astronomical unit
Plural form: astronomical units
Symbol: AU
Category type: length
Scale factor: 149597870700
The SI base unit for length is the metre.
1 metre is equal to 6.6845871222684E-12 astronomical unit.
Valid units must be of the length type.
You can use this form to select from known units:
The astronomical unit (AU or au or a.u. or sometimes ua) is a unit of length defined to be exactly equal to 149,597,870,700 metres. Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its modern redefinition.
The symbol "ua" is recommended by the Bureau International des Poids et Mesures, but in the United States and other anglophone countries the reverse usage is more common. The International Astronomical Union recommends "au" and international standard ISO 31-1 uses "AU".