Each product page has the exact measurements of the piece in its description.
Better Bodies and GASP follow the same sizing - the sizes are accommodating to any body type, as they are designed to fit in bigger bodies. Bodybuilders are essentially the target audience of GASP, fitness people of all kinds are the audience of Better Bodies. Gorilla Wear is a brand of bodybuilders, however its sizing is slightly different: you will find your size, but it is not necessarily matching that of GASP. Gorilla Wear runs in particular ladies, smaller. Lithe and taller/narrower people are well catered by Gorilla Wear ladies' range.
Really big guys you'll find your perfect match from GASP and Better Bodies clothing. Gorilla Wear will fit you fine, but you will likely see different size suiting you as GW tees have more narrow cut and particular. In bottoms you are catered by all three brands smoothly!
For medium and small size bodies all three brands are great in entirety in both tops and bottoms. Better Bodies and GASP have uniform sizing across the board.
GASP and Better Bodies cater all size bodies on ladies' clothes as well. GASP clothing line has a great unisex audience as well- in fact it is very common to see ladies in GASP tee and Better Bodies high pants/leggings!
Gorilla Wear ladies range runs little smaller. Gorilla Wear women's range is the most optimal for petites and smaller bodies, but also medium size bodies will find their match from them. Gorilla Wear Large would roughly correspond to Better Bodies Medium.
Gorilla Wear generally likes their tees shorter than GASP/Better Bodies and their tees are more often than not, shorter at the hem.
Noteworthy is that bigger ladies will find their leggings from Better Bodies no matter what.
Measurements you may need are as follows:
Chest: Measure around the fullest part of your chest from on top of the nipples. Ladies can use the measurements of well fitting regular bra!
Waist: Measure around the narrowest part of your midsection.
Lads: Its where the waistband of your pants would be.
Ladies: It's your narrowest part of your in your midsection
Hips: Measure around the widest part of your hip area. Make sure your butt from thickest point fits within the measurement if it's a garment that goes on top of your butt.
Lads: Along your bony bits that can poke out.
Ladies: Same, where your hipbone flares.
Inseam: From your groin to top of the ankle on both.