A steering wheel can typically turn between about 972 and 1152 degrees, or about 2.7 to 3.2 full rotations. The actual amount that your wheel can turn will depend on your car and the age of your vehicle.
However, it’s not recommended that you turn your steering wheel all the way. Doing so can wear out your steering mechanisms, which can eventually lead to a broken steering wheel. The same goes for turning your wheel while stationary, since this also puts unnecessary pressure on your steering mechanism.