What size orthopedic bed does your dog actually need?

Almost every complaint about an orthopedic dog bed is a sizing complaint wearing a different hat. "The foam went flat" is often a 90-pound dog on a bed rated for 70. "He hangs off the edge" is a dog measured while curled and bought while stretched. "She won't get on it" is a bolster the height of her hock. None of those are foam problems. They are tape-measure problems, and they cost you a return.

This page is the arithmetic we do before recommending a size on any of our bed roundups. It takes about four minutes and a tape measure.

Step 1 — measure the dog stretched out, not curled

Wait until your dog is asleep on their side with their legs extended, which is the position that needs the most room, and measure from the tip of the nose to the base of the tail — the tail itself does not need to be on the bed. Then measure the widest point across the body, usually the shoulder or hip.

Now add. Our rule of thumb, and it is a rule of thumb rather than a manufacturer standard: add 6 inches to the length for a dog under 40 pounds, and 8 to 12 inches for a dog above it. That margin is not luxury. A senior dog changes position more often during the night than a young one, because lying on a sore hip for four hours is no longer possible, and every one of those position changes needs somewhere to go.

A specific and common failure: owners measure a dog that has been curling up tightly for months because the bed is too small, buy the same size again, and conclude their dog likes small beds. A stiff dog curls to fit the space available. Give a bed with room and watch what happens over the following fortnight before deciding what your dog prefers.

Step 2 — pick foam depth by weight, not by bed size

Length and foam depth are two separate decisions, and manufacturers rarely separate them for you. A large bed can be thin, and it very often is — the footprint grows while the foam stays where it was.

What matters is whether your dog bottoms out: whether the hip that carries the weight reaches the hard floor through the foam. You can test this on a bed you already own. Press down hard with a flat palm where the dog's hip sits. If you can feel the floor through the foam with the pressure of one arm, a sleeping 80-pound dog has been feeling it all night.

We deliberately have not printed inch figures for foam depth in that table. Depth is only meaningful next to foam type — three inches of solid support foam and three inches of shredded fill are not the same object — and every manufacturer measures it differently. Read the listing, find out what the core actually is, and be skeptical when a listing describes the total loft of a bed rather than the depth of its support layer. Our memory foam page covers how to tell the two apart on an Amazon listing.

Step 3 — check the entry height, which no size chart mentions

A size chart tells you the footprint. It does not tell you the one measurement that decides whether an arthritic dog uses the bed: how high they have to lift a back foot to get on.

For a stiff dog, the useful comparison is their hock — the backwards-bending joint on the hind leg. If the front edge of the bed is above that, getting on requires a deliberate step-up with a joint that hurts, and some dogs will simply decline. This is why a 360-degree bolster bed can be a poor buy for exactly the dog it is marketed to, and why our bolster bed page ranks by rim height as much as by foam.

If your dog has already stopped using a bed they used to like, measure the front edge before you blame the foam. And if they have stopped using a bed that sits on a slick floor, the problem may be the approach rather than the bed — a dog that has slipped while stepping onto a bed remembers it. Our guide to floor traction covers that.

Step 4 — size for the room, and for the wash

Two practical constraints that are easy to forget in a shopping cart:

• Where it goes. Measure the floor space, particularly if the bed is destined for a spot beside a sofa or in a hallway a person also walks through. A bed pushed against a wall gives a dog a side to brace against when standing up, which is genuinely useful for a weak-hipped dog.
• Whether the cover fits your machine. A large bed cover is a large object wet. If a senior dog has any incontinence, the cover comes off often, and a cover that needs a laundromat gets washed less than one that fits a domestic drum. Check the cover washing instructions before the bed dimensions.

The size-up question

Should you buy one size larger than the chart says? Usually yes, with one exception.

Yes, because manufacturer charts tend to describe the dog that will physically fit rather than the dog that will be comfortable, and because the cost difference between adjacent sizes is small next to the cost of returning a bed. Yes also because a senior dog often has a companion who joins them, or an owner who sits on the edge.

The exception is a dog that seeks contact and security — a small, anxious, or vision-impaired senior who wants walls. For that dog a too-large open bed can feel exposed and go unused. That is a real preference rather than a stiffness problem, and it is covered on our calming bed page, honestly assessed.

The four-minute version

1. Measure nose to tail base with the dog stretched out. Add 6 inches under 40 lb, 8 to 12 inches over.
2. Match the support core to the weight, and read what the core actually is.
3. Compare the front edge height to your dog's hock.
4. Check the cover fits your washing machine, and the bed fits the room.