Mens Stormbreak Waterproof Overtrousers

Leg length please

My husband has a waist and inside leg measurement of 34 ins. The medium size is no good for him, so what about the large size? What do they measure?

Does the size take into account the trousers underneath? What I am asking is that if I am usually an S, would I need to order an M?

Hi I am 42 waist 29 leg do I need xl or xxl