Pets Calculators
Dog sizing runs on a tape measure, not a weight column, and the three things you buy first each run on a different measurement: a collar on the neck, a harness on the chest, a crate on length and height. None of them can be derived from the others, and the direction that gets you in trouble changes with each one.
- Dog Collar Size ChartNeck circumference to XS through XXL, with breed starting points.
- Dog Crate Size Chart18 to 48 in by length and height. Oversizing breaks house training.
- Dog Harness Size ChartChest girth to XS through XL. Too big is the dangerous direction.
Three measurements, and none of them is the dog's weight
Almost every dog sizing chart online opens with a weight column, because weight is the number an owner knows without fetching a tape. It is a proxy, and not a good one. Two dogs at 60 lb can be several inches apart at the chest depending on build, and a harness only cares about the girth it has to close around.
Each of the three things here runs on a different measurement, and no one of them can be derived from another:
- Collar: neck circumference, taken where the collar sits, below the jaw and above the shoulders.
- Harness: chest girth, taken around the widest part of the ribcage just behind the front legs.
- Crate: length and height, nose to the base of the tail, and floor to the top of the head with the dog sitting.
A dog can be a large collar and a medium harness at the same time, and nothing has gone wrong. They are two different circumferences on two different parts of the same animal.
The mistake changes direction depending on what you are buying
This is the thing that makes dog sizing harder than it looks, and it is why these are three pages rather than one chart. The dangerous direction is not the same for all three.
| Item | Sized by | The dangerous direction | Why |
|---|---|---|---|
| Collar | Neck circumference | Too tight | Restricts the throat |
| Harness | Chest girth | Too loose | A frightened dog reverses out of it |
| Crate | Length and height | Too big | Breaks house training |
The crate one surprises people most. Crate training works because a dog will not soil where it sleeps, so a crate with a spare corner has somewhere that is not the bed. Buy it roomy out of kindness and you have removed the mechanism that made it work.
Buying for a puppy, and the one place the rule flips
A puppy cannot be sized from its breed, because the breed describes an adult the dog will not be for the better part of a year. That holds for a collar and a harness, and it is why both of those pages refuse to give a puppy a breed-based size at all. Measure what you have today, buy cheap and adjustable, and expect to replace it.
A crate is the exception, and the reason is hardware rather than principle. Crates ship with a divider panel, so you buy the adult size, panel it down to the space the puppy needs now, and move the panel out as they grow. One crate instead of three, and the house training keeps working the whole way through.
Why breed is an input here and a starting point everywhere
Roughly a quarter of dog sizing searches are phrased by breed rather than by measurement. Nobody types "18 inch neck", they type "what size collar for a border collie". All three tools here accept a breed for that reason, and all three label the answer a starting point rather than a fitting.
The spread within a breed is genuinely a whole size. Two German Shepherds of the same age and the same breeding can differ by a couple of inches at the neck, and chest girth varies more than neck girth does, which is why harness returns outnumber collar returns. Use the breed mode to know what to expect before the dog arrives. Use the tape before you buy anything you cannot return.
How to measure a dog that will not stand still
A soft sewing tape is the right tool for the two circumferences, because a rigid tape will not follow the curve and reads short. String against a ruler works just as well: mark where it meets, lay it flat, measure. For the crate you want the opposite, a rigid tape, since those are two straight lines rather than curves.
Measure with the dog standing for the harness, because a sitting dog's ribcage is a different shape from the one that will be wearing it. Measure sitting for crate height, because sitting is the tallest a dog gets inside a crate. And measure snug against the fur rather than compressing it, on everything.
Letters do not travel, and inches do
Collar and harness sizes are letters, and no standards body governs them, so one maker's medium is another's large. What travels is the published range in inches or centimeters, which every product worth buying prints on the listing. Read that and ignore the letter, which is the same advice as on our human letter size chart, for the same reason.
Crates are the exception and the easiest of the three to buy: they are sold by nominal length in inches, and an 18, 24, 30, 36, 42 or 48 means roughly the same thing everywhere. Check whether a listing quotes internal or external dimensions though, because that difference is real and it is usually external.
Frequently asked questions
Can I size a dog by weight?
Not reliably, and the charts that let you are handing you a proxy instead of a measurement. Two dogs at 60 lb can be several inches apart at the chest depending on build, and a harness only cares about the girth it has to close around. Weight is the right input for diapers and for dog food. For anything that wraps around the dog, use a tape.
Is a dog's collar size the same as its harness size?
No, and there is no reason to expect it to be. A collar is sized on neck circumference and a harness on chest girth, which are two different circumferences on two different parts of the same animal. A dog can be a large collar and a medium harness at once. Deep-chested breeds show the gap most.
What size crate does my dog need?
Body length plus about four inches, and sitting height plus about two, then round up to the nearest crate that clears both. Either measurement can decide it: a Dachshund is long on short legs so length wins alone, while a tall square-built dog can need two sizes up for headroom on identical length. Our crate chart names which one drove your answer.
Should I buy a bigger size so my puppy can grow into it?
For a collar or a harness, no. A harness a puppy can grow into is one the puppy reverses straight out of, usually at a roadside. For a crate, yes, and that is the one place the rule flips: crates ship with a divider panel, so you buy the adult size, panel it down to what the puppy needs now, and move it out as they grow.
How do I measure my dog for a collar or harness?
Use a soft sewing tape, or string laid against a ruler afterwards. For a collar, measure the neck where the collar sits, below the jaw and above the shoulders. For a harness, measure the widest part of the ribcage just behind the front legs, with the dog standing. Snug against the fur, without compressing it.
Are dog sizes standard between brands?
The letters are not. XS through XL mean whatever each maker decides, which is why harness returns are so common. What travels is the published range in inches or centimeters, and every listing worth buying prints it. Crates are the exception: they are sold by nominal length, so an 18, 24, 30, 36, 42 or 48 means roughly the same thing everywhere.
Can I size my dog from its breed?
As a starting point, yes, and all three tools here take a breed for exactly that reason. As a fitting, no. The spread within a breed is genuinely a whole size, and chest girth varies more than neck girth does. Use the breed mode to know what to expect before the dog arrives, and the tape before you buy anything you cannot return.
Which is the dangerous direction to get wrong?
It changes by item, which is the reason these are three separate charts. A collar is dangerous too tight, because it restricts the throat. A harness is dangerous too loose, because a frightened dog reverses out of it. A crate is dangerous too big, because a spare corner gives the dog somewhere that is not the bed and house training stops working.
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