Measure your dog’s width at the shoulders and its height from the top of the back, just behind the head, to the bottom of the chest. Ideal Pet says the door’s flap opening should be both wider and taller than those measurements.
How to measure
- Width (A): across the widest point of the shoulders. Ideal Pet suggests adding a little if your dog is wider somewhere else.
- Height (B): from the top of the back, just behind the head, to the bottom of the chest.
- Compare: pick a flap opening wider than A and taller than B.
- Withers: from the floor to the top of the shoulder, for how high to mount the door (Endura Flap, below).
Ideal Pet Designer Series Ruff-Weather
| Size | Model | Flap | Cutout | Pet weight |
|---|---|---|---|---|
| Small | DSRWS | 5 x 9¼ | 6½ x 11¼ | 2–12 lb |
| Medium | DSRWM | 7¼ x 13 | 8⅜ x 15 | 13–35 lb |
| Extra Large | DSRWXL | 9¾ x 17 | 11⅛ x 19¼ | 36–90 lb |
| Super Large | DSRWSL | 15 x 23½ | 16¼ x 25¾ | 91–120 lb |
The size picker on the same page calls the 9¾ x 17 in flap Large, where the table calls it Extra Large. Order by the flap size to be sure.
PetSafe Extreme Weather Pet Door
| Size | Pet size | Flap opening | Frame | Cut out |
|---|---|---|---|---|
| Small | Up to 15 lb | 5⅛ x 8¼ | 7½ x 11 | 6⅜ x 10⅛ |
| Medium | Up to 40 lb | 8⅛ x 12¼ | 10½ x 15 | 9⅜ x 14 |
| Large | Up to 100 lb | 10⅛ x 16¼ | 12½ x 19⅞ | 11⅜ x 19 |
Weight bands don’t line up
A 40 lb dog is at the top of PetSafe’s Medium, with an 8⅛ x 12¼ in flap, but in Ideal Pet’s Extra Large, with a 9¾ x 17 in flap. Go by your dog’s measurements rather than its weight.
How high to mount it
Endura Flap, a pet door maker, says the top of the flap should ideally be at least as tall as your dog at the withers, the top of the shoulder. The step-over, the height of the bottom of the door above the ground, is what lifts the flap that high.
| Flap height | Step-over needed | Top of the flap |
|---|---|---|
| 15 in | 7 in | 22 in |
| 19 in | 3 in | 22 in |
Endura Flap says the shorter the step-over, generally the better, because older or arthritic dogs find a high one harder to manage. You can choose the step-over when you fit a door into a door or wall, but on most patio panels it’s fixed.