What size pet door do I need?

Measure your pet's shoulder height and chest width and add roughly two inches of clearance. Most collar-key doors in this roundup are sized for small-to-medium pets up to ~15 lb (PetSafe Electronic, SureFlap) or for medium-to-large dogs up to 100 lb (Power Pet). For dogs over 100 lb, you'll need a wall-mount XL door specifically rated for that weight class.