I bought the 2-4 y/o size small. My 5 y/o daughter fit perfectly with some room to spare (they weren't tight). She is 43 lbs and 46  slim/average waist. I thought these boy short-looking  undergarments would be great to wear under skirts as a bloomer over underwearbut def not! They are less than 1.5 in length around the thigh come up around the legs once worn they are def underwearsuper cute though for underwear and she said they were very comfortable! Would buy these again but more as underwear though!