How to measure your dog

What you need

• A soft tape measure, the sort used for sewing. It follows the curve of a rib cage, which a rigid tape cannot.
• Or a piece of string and a ruler. Wrap the string, pinch where it meets, lay it flat and measure the pinched length. This is just as accurate and most households already have both.
• A second person, if your dog will not stand still. Every measurement on this page assumes a dog standing square on all four feet. A sitting or lying dog gives a different, useless number.
• Somewhere to write it down, in inches or centimetres. Pick one unit and stay with it. This site shows both and the toggle at the top of the page switches every number on it.

Measure twice. A tape that has slipped an inch is the most common reason a size turns out wrong, and an inch matters: this site treats anything within 1 in of the edge of a size as “between sizes”, because that is how close the bands are. If two attempts disagree, measure a third time and use the larger.

1. Chest girth — for a harness

This is the one that matters most, because every harness on this site is sized on it. Stand the dog square. Find the deepest part of the rib cage, which on most dogs is immediately behind the front legs, and pass the tape all the way around the body there. Keep it level: a tape that slides back towards the waist reads several inches small.

Snug but not tight. Two fingers should slide under it comfortably. Pull it tight and you will buy a harness that is tight on the dog.

Makers describe the same spot in slightly different words, which is worth knowing when you compare charts. 2 Hounds Design calls it “chest girth (largest part, right behind front legs)”; Blue-9 asks for ribcage girth about two inches behind the elbow; Ruffwear says the widest part of the rib cage. They are all the same loop.

Put the number into the harness calculatorand it checks all 19 published harness charts at once, orread the charts yourself.

2. Neck — for a collar

Measure where a collar actually sits, which is the base of the neck, not up behind the ears. On a dog that already wears a collar, measure where the collar has worn the coat. PetSafe is the exception worth knowing about: for its martingale it asks for the measurement “neck (top of neck, directly behind the ears)”, because a martingale has to pass over the head.

Two fingers under the tape again. Wild One puts the same rule in its own instructions: it sizes the collar by “neck circumference (widest part, two fingers' room)”.

A neck measurement is also worth taking even if you are buying a harness. Several makers publish a neck range alongside the chest range, and a dog whose neck falls outside it can be a poor fit in a size the chest measurement says is right. The calculators flag that where the maker publishes both.

Put the number into the collar calculator, or compare the 7 collar charts.

3. Length — for a crate

Nose to the base of the tail, with the dog standing. The base of the tail, not the tip: the tail does not need crate space and including it buys a crate a size too big. Measure in a straight horizontal line rather than following the curve of the back.

Frisco publishes the same method on its own crate page: “measure nose to base of tail (standing) and top of head to floor, then add 4 in. 'Max Length/Max Height' is the largest dog size the maker suggests.”

Source: Frisco (Chewy), Fold & Carry Single Door Collapsible Wire Dog Crate, checked Nov 4, 2026.

4. Height — for a crate

Floor to the top of the head, standing. If the ears stand up, measure to the ear tips: a crate a dog has to duck to enter is a crate the dog will avoid. Note that this isnot the height breed standards give. AKC heights are measured at the withers, the ridge between the shoulder blades, which is lower than the head. The breed figures on this site are withers heights and are labelled as such; a crate needs the head measurement.

Then add 4 inches to both the length and the height. That is the room a dog needs to stand without ducking, turn around, and lie flat on its side. The AKC puts the allowance at“add 3 to 4 inches”; this site uses 4, the top of that range, because a crate slightly too big costs much less than one slightly too small.

One trap: compare your result against the crate’s interior. Makers do not agree on what the number on the box means, and some publish the overall outside size.The crate calculator handles thatfor all 6 charts, orread them side by side.

Weight, and why it is the last resort

Weight is easy to get and tells you least. Two dogs of the same weight can be different shapes, and a harness goes round a shape. This site uses weight only where a maker publishes weight bands and no girth exists for the dog in question, and every answer that came that way is labelled by weight only, less reliable.

Crates are the exception where weight is genuinely useful, because makers publish weight guidance for them and a crate is a box rather than a garment. Even there it is the rougher route: the length and height are what decide whether a dog can stand up and turn around.

Which measurement each thing is sized on

Counts come from the 32 charts on this site, all read 2026-11-04.

Puppies: measure again

A puppy’s measurements go out of date in weeks. Measure a growing dog roughly once a month, and check the fit of a harness every time: a strap that was snug in March can be tight in June. Buy the harness and collar for the dog in front of you, because an adult-sized harness on a puppy slips, and a harness that slips is one a dog can back out of.

The crate is the exception and goes the other way. Buy the size the dog will need as an adult and use the divider panel to shrink it, moving the panel back as the dog grows. A crate sized to a puppy is outgrown in a month, and a full-size crate with no divider gives a puppy room to use one end as a toilet.