A petametre (American spelling: petameter, symbol: Pm) is a unit of length equal to 10¹⁵ metres.

Petametres could be used for measuring interstellar distances, but astronomers have been long accustomed to using light-years (about 9.5 petametres) and parsecs (about 31 petametres) instead.

• 1 Pm is equal to 6685 AU
• 1 light-year is equal to 9.46 Pm
• 1 parsec is equal to 30.86 Pm
• the distance to Proxima Centauri is 40 Pm
• the distance to Sirius is 81 Pm
• the distance to Vega is 237 Pm
• light travels the distance of 1 Pm in 38.6 days (38 d 14 h 34 min 1 s)

terametre << petametre << exametre

See also

• 1 E15 m
• SI
• SI prefix
• Orders of magnitude