Tank
Most modern tanks most often have four crew members, or three if an auto-loader is installed. These are the:
Historically, crews have varied from just two members to a dozen. For example, pre-World War II French tanks were noted for having a two-man crew, in which the overworked commander had to load and fire the gun in addition to commanding the tank. First World War tanks were developed with immature technologies; in addition to the crew needed to man the multiple guns and machine guns, up to four crewmen were needed to drive the tank: the driver, acting as the vehicle commander and manning the brakes, drove via orders to his gears-men; a co-driver operated the gearbox and throttle; and two gears-men, one on each track, steered by setting one side or the other to idle, allowing the track on the other side to slew the tank to one side.
Platoon
Tank platoons prior to the late 1980s consisted of a platoon headquarters squad and three tank squads, each consisting of one T-64, T-72 or T-80 tank for 12 personnel and 4 tanks total; platoons that used the older T-54, T-55 or T-62s added another crewmember for a total of 16. However, tank units operating in Eastern Europe began to standardize their platoons to just two tank squads, for a total of 3 tanks and 9 personnel.