The coherent SI unit of acceleration is the metre per second squared, m/s2.

The unit in the imperial system for acceleration is the foot per second squared, ft/s2

Factors in bold are exact.

Convert From To Multiply Std
kilometres per second squared km/s2 m/s2 1000 2
gal (galileo) Gal m/s2 0.01 2
milligal mGal m/s2 1.0 x 10-5 2
acceleration of free fall, standard gn m/s2 9.80665 1
inch per second squared in/s2 m/s2 0.0254
foot per second squared ft/s2 m/s2 0.3048 1

1: BS 350:2004 Table 14

2: BS 350:2004 Section 14