"Runs small" shows up in a lot of harness reviews. Most of those come down to guessing the size instead of measuring, and measuring takes a soft tape and a couple of minutes.
How do you size a dog harness? Measure the chest at its widest point, just behind the front legs, with a soft tape held snug but not tight. Pick the size whose chest range covers your number. If the number sits near the top of a range, go up one size. Size charts aren't shared between brands, so use the chart from the maker of the harness you are buying.
How do you measure a dog for a harness?
You need two numbers. Have your dog stand up straight (a treat helps) and measure in this order.
- Chest (girth): wrap the tape around the widest part of the rib cage, just behind the front legs. PetMD gives the same spot: around the widest part of the rib cage. This is the number you size by.
- Neck: measure around the base of the neck, where a collar would naturally sit, not up near the ears.
Keep the tape snug against the coat. You should be able to slide two fingers flat under it. No soft tape? Wrap a piece of string or a phone charging cable around the chest, pinch the spot where it overlaps, then lay it flat against a ruler.
HAVLIN dog harness size chart
Size by chest first. If your dog falls inside two sizes, check the neck too.
| Size | Chest | Neck | Approx. weight |
|---|---|---|---|
| XS | 11.8 – 16.9 in (30 – 43 cm) | 9.4 – 13.0 in (24 – 33 cm) | 2 – 6.5 lb |
| S | 16.5 – 23.6 in (42 – 60 cm) | 11.0 – 15.7 in (28 – 40 cm) | 5.5 – 16.5 lb |
| M | 22.8 – 31.5 in (58 – 80 cm) | 13.8 – 21.7 in (35 – 55 cm) | 15 – 44 lb |
| L | 30.7 – 40.2 in (78 – 102 cm) | 19.7 – 25.6 in (50 – 65 cm) | 44 – 88 lb |
Weight is a rough guide only. Measurements are taken by hand and can vary slightly.
Worked example. A dog with a 24 in chest is past the top of size S (23.6 in), so it falls in M (22.8 – 31.5 in). A dog with a 16.7 in chest sits in the overlap between XS (up to 16.9 in) and S (from 16.5 in). Use the neck number and the next section to decide.
What if your dog is between two sizes?
- Chest near the top of a range: go up a size. The straps tighten down more comfortably than they stretch up, and PetMD says the same: choose the larger size if your dog is right on the cusp.
- Puppy still growing: pick the size that fits now, with some strap left to tighten, and plan to re-measure. A harness that is too big on a small puppy is easy to slip out of.
- Very fluffy coat: measure through the fur, not flattened against the skin.
- Deep chest, narrow waist (greyhounds, whippets, some doodles): size by chest, then tighten the belly straps.
Why do harnesses so often end up too small?
| Mistake | What happens |
|---|---|
| Buying by weight alone | Two 20 lb dogs can have very different chests. A deep-chested dog and a slim one will not fit the same harness. |
| Guessing instead of measuring | Most of us underestimate how wide a dog's chest is, especially under a fluffy coat. |
| Pulling the tape tight | You get a number with no room for movement or breathing. |
| Mixing units | Many harnesses are made overseas, and the chart may be in centimeters. Converting in your head is where errors creep in. The chart above gives both. |
Reviews point the same way. In our own keyword count of 597 Amazon reviews across 22 harness listings (pulled Oct 2026), 89 of the 343 reviews rated 1 to 3 stars mentioned sizing or fit in some way: 49 said "too small" or "runs small," and 19 said "too big," "too large" or "runs big." We pulled low-star and high-star reviews separately, so this is not a rate for the whole market.
How can you check the fit once it arrives?
- Adjust the straps so the harness sits flat, with no twisting.
- Slide two fingers flat under each strap. Two should fit, but not your whole hand.
- Walk your dog for a few minutes, then look under the front legs. There should be no rubbing or red marks.
- Gently pull the harness forward toward the head. It should not slide over the ears.
The two-finger check is the common rule: the AKC says you should be able to fit two fingers under the straps. We go through it step by step in How to Fit a Dog Harness So Your Dog Can't Back Out of It. If the straps leave marks behind the front legs, see dog harness rubbing under the arms.
How often should you re-measure?
Re-check the fit whenever your dog's body changes: a growth spurt in a puppy, weight gained or lost, or a fresh haircut on a fluffy dog. A harness that fit in spring can be loose by autumn.
Dog harness sizing FAQ
Should I size a dog harness by weight or by chest?
By chest. Weight is only a rough guide, because dogs of the same weight can have very different chest sizes.
Where exactly do I measure the chest?
Around the widest part of the rib cage, just behind the front legs, with the dog standing.
My dog is between two sizes. Which one should I pick?
Go up a size and tighten the straps. If you are still unsure, email us your dog's chest and neck measurements and breed, and we will suggest one.
How do I measure a dog without a tape measure?
Use a string or a phone charging cable. Wrap it around the chest, mark the overlap, then measure the string against a ruler.
Is a HAVLIN size M the same as an M from another brand?
Not necessarily. Charts differ between brands, so compare your dog's chest to the chart of the harness you are buying.
What if the harness doesn't fit?
Email us within 30 days of delivery and we will help you exchange it for another size or refund it. Items need to be unused.
Still doesn't fit?
Email us within 30 days of delivery and we'll swap the size or refund you. The set needs to be unused, and return shipping is on you unless the item is defective. Full details are in our refund policy.
If you land between two sizes, take the bigger one and swap within 30 days if it's loose. You get the harness, collar, leash and a bag holder in one of 10 colors; the holder comes empty, so bring your own bags. US shipping is free, but allow about 12 to 25 business days.