If you are between sizes, measure first and follow the size chart for that exact model.
Helmets (Riddell, Schutt)
If your head measurement lands between sizes, start with the smaller size for a snug fit, then fine tune with the fit system or air liners.
Shoulder pads
Choose the size that gives correct coverage and still lets you move freely. If in between, pick the one that stays secure without restricting your shoulders.
Gloves (Nike and others)
Match your size to palm width and hand length. Gloves should feel snug and will break in.
Cleats (adidas, Nike and others)
Go up 0.5 size in US sizing and 1 size in EU sizing as a standard guideline for the best fit.