Ok, I know it's ridiculous that I don't know this, but I seem to have spent the last decade in yoga pants and I am really trying to smarten myself up. I ordered some straight leg trousers in navy and black - maybe even slightly tapered at the bottom but not hugely so. They have little notches on the outside of the leg at the ankles. I think I actually look quite nice in them ,but have no idea what length I need. In flats, the 31 touches the top of the shoe at the back, at the front, it's leaving a fair expanse of foot exposed. There is no excess material folding over my foot - it just stops. The 33 covers the back of the shoe (but doesn't touch the floor) and covers most of the front of my foot down to the shoe. Because it's resting on the foot, the notch on the ankle is opening up, and there is def a fold in the material. I was thinking the longer one, but I'm not sure if that's me playing safe. Please help me, as I'd like to return the two pairs I don't need today, and get that £100 back on my credit card! If it makes a difference, I never wear heels, these would be worn with ballet flats, brogues or ankle boots.