The single most common reason a dog ignores a new bed is that it's too small. She can't stretch out, so she goes back to the floor. Here's how to get the size right the first time.
Measure her stretched out
Wait until she's lying on her side with her legs extended, then measure from her nose to the base of her tail. Write the number down, she won't pose twice.
Add about 6 inches
A dog needs room to sprawl, twist onto her back, and change position through the night. Adding roughly six inches to her measured length gives her that room without the bed swallowing your floor.
Use weight as a sanity check
Weight ranges are a guide, not a rule. If her measured length and her weight point at different sizes, trust the length. And if she's between sizes, older, or a sprawler, size up.
Our full size guide has the measurements for every size, and the beds themselves are here.