The best way to read our size guide is to just go by the UK/US/EU size and remember there are no buttons or zips on the waist so you need to be able to pull them up over your thighs and bottom which is why the waist size is larger then the actual size.
The cotton twill naturally come up smaller than the stretch twill so please go by the size guide above. They don't have stretch so if you go too small they won't pull up over your thighs and bottom.
What the HECK is twill?
Twill is a type of fabric with a pattern of diagonal parallel ribs.
There are fewer interlacings in twill as compared to other weaves which allows the yarns to move more freely, and therefore they are softer and more pliable. Twills also recover from creasing better than plain-weave fabrics do so less ironing needed.
Twills are durable, and is air- and water-resistant. Basically it's a thicker cotton, meaning you can move, bend and get them on and off easily. It is thinner than corduroy so a nice weight for warmer weather.