Servos rotate from 0 (far left) to 180 (far right) degrees. If you try more, you might damage the servo. As for calculating the pulse per degree, it's easy. You specify the pulse lenght in microseconds, so for a full sweep (180 degrees) the pulse goes from 1000us to 2000us (sometimes actually the timing is different, like from 500 to 2500, you need to experiment with your servos). You divide the difference by the number of degrees traveled and you get the pulse lenght per degree, in this example 1000/180=5.5555. That means you can increment the pulse lenght by 5.5us to step one degree.