help with M&S slip lengths

[taralee]

Very dull thread - sorry
I want to buy a slip from M&S to wear under dresses. a dress type-one rather than waist only IYSWIM.
The sizing is very confusing. If you look at this slip
you will see what I mean. If you click on sizing it has the dress size (e.g. 8, 10, 12 etc) followed by another number which is presumably the length??

But I don't know if it's centimetres or inches or where to measure from!

I want a mid thigh length and am size 8 and 5'6".

Can anyone help me?

I think it might be the length in inches from the waist like a skirt length, so if you wanted mid thigh you would need 16" as 19" would probably be just above the knee.

ah - tht makes sense!