Convert parsec to foot

The inch has been exactly 2.54 cm since 1959; 12 inches make a foot, 3 feet a yard and 1,760 yards a mile of 1.609 km. The US and UK still use them for heights (5 ft 10 in is 178 cm), road distances and speed limits, and the inch survives everywhere in screen sizes, wheel rims and pipe threads. Five miles are almost exactly eight kilometres, a handy road-sign rule.

The astronomical unit is the mean Earth–Sun distance, fixed at exactly 149,597,870.7 km: Mars orbits at 1.5 au, Neptune at 30. The light-year is the distance light travels in a Julian year, 9.46 trillion km, and the light-second 299,792 km, about three quarters of the way to the Moon. The parsec, 3.26 light-years, is the distance at which the Earth's orbit spans one second of arc, and is what astronomers actually use: the nearest star is 1.3 pc (4.2 ly) away, the centre of the Milky Way about 8 kpc.