The volume required for 14 AWG conductor is 2 cubic inches. If I have a simple case of 14/2 going in and 14/2 going out, with 1 switch and 1 clamps, I get a volume of 16 cubic inches:

4 conductors = 8 cubic inches

1 clamps = 2 cubic inches

1 device = 4 cubic inches

1 ground = 2 cubic inches

These 15 cubic inch boxes are pretty common but it seems you can only get one 14/2 wire into this box. What do electricians do when they need to have one 14/2 wire in and one 14/2 or even two 14/2 out on a single gang? What happens if you need to bump up the gauge to 12/2 or you have a 3-way switch and need to use a 14/3 wire with a 14/2?

Thanks.