Find your favourite fitting leggings at home. Lay them flat, unstretched on a flat surface
Measure across the hip (usually where the seam is), the waist (top of garment) and inseam (from the crotch to the bottom of the legging).
Double the hip and waist values and compare measurements. Remember worn leggings will be larger than brand new ones. Our measurements are approximate, so yours should be too. Keep in mind, the dimensions measured laying flat WILL be smaller than if you measured yourself with a tape. Bear in mind the material is stretchy and they are form fitting. They are designed to mould to the body so don't worry if it is off by a bit. Remember you can always exchange if it's not the right size.