A crate should let a dog stand up without its head or ears touching the roof, turn around, and lie flat on its side. Much bigger than that and a young dog may use one end as a toilet; smaller and it is uncomfortable. Crates are sold by length in inches, so the calculator turns two measurements of your dog into the smallest standard size that meets the usual rule: body length plus two to four inches, and sitting height plus two to four inches. For flying, airlines follow the IATA Live Animals Regulations, which use a different formula — switch to Airline above.
Length (A): with your dog standing, measure from the tip of the nose to the base of the tail — where the tail joins the body, not the tip. Height: with your dog sitting, measure from the floor to the top of the head, or to the tips of upright ears if they are higher.
For an airline crate you also need the height from the floor to the elbow (B), the width across the shoulders at the widest point (C), and the standing height to the top of the head or ear tips (D). A soft tape measure and a second person make this much easier.
Common US wire crates are sold in 18, 22, 24, 30, 36, 42, 48 and 54 inch lengths. The calculator picks the smallest that is at least your dog's length plus two inches. Heights vary by brand for the same length, so check the listed interior height against the minimum shown — frames and trays make the inside smaller than the outside dimensions suggest.
For a puppy, buy for the adult size and use a divider panel, moving it back as the puppy grows. Our puppy weight calculator gives an adult-size estimate; for a mixed breed, the parents' size is the best guide.
The IATA formula for a dog's container is: interior length at least A plus half of B; interior width at least twice C; interior height at least D, so the dog can stand without touching the roof. Airlines also require a rigid container with ventilation on several sides, a secure door and no wheels in use during the flight.
Airlines add their own rules on top — breed restrictions for short-nosed dogs, maximum crate sizes for the aircraft, and cabin limits. Always confirm with the airline before booking, and let your dog get used to the crate for weeks before travel.
A crate should never be used as punishment. Feed meals in it, leave the door open with a comfortable bed inside, and build up short periods with the door closed while you are at home.
Adult dogs should not be crated for most of the day. If your dog whines, pants heavily, drools or tries to escape, it may be anxious rather than untrained — slow down, and talk to your vet or a qualified behaviourist if it persists.
Measure nose to base of tail and add two to four inches for the length; measure sitting height to the top of the head or ears and add two to four inches for the height. Then pick the smallest standard crate at least that long, and check its interior height.
Yes, for a dog that is still being house-trained, because it can toilet at one end and sleep at the other. Use a divider panel for a puppy. For a fully house-trained adult, a slightly larger crate is fine.
IATA uses four measurements: A, nose to root of tail; B, floor to elbow; C, width across the shoulders; D, standing height to the top of the head or ears. The crate interior must be at least A + ½B long, 2 × C wide and D high.
One sized for the dog it will become, with a divider to keep the usable space small at first. Estimate the adult size from the breed or the parents, or with a puppy weight calculator.