The smallest watch movement is Cal.G720, developed and manufactured by Citizen Watch Co., Ltd. (Japan) in 2002, which measures 30 mm² (0.046 in²) in surface area and 73 mm³ (0.004 in³) in volume.

Watch movement means machine parts of a watch except for exterior parts, such as a case, a dial and hands.

Its full dimensions are 5.0 mm x 6.0 mm x 2.5 mm.