A harness only works when it fits: too loose and a dog can back out of it, too tight and it rubs behind the front legs. The good news is that measuring takes two minutes and one soft tape.
Two numbers matter. Chest girth decides the size; neck girth confirms that the neck opening will sit comfortably. Measure both, then compare them with the size chart below.
What you need
A soft measuring tape (or a piece of string you can lay flat against a ruler afterwards), a few treats, and a calm moment with your dog standing on all four feet. Measure directly against the coat — snug, not tight.
Step by step
- 01Stand your dog square. Sitting or lying down changes the shape of the chest and gives a smaller number.
- 02Measure chest girth: wrap the tape around the widest part of the ribcage, just behind the front legs. Keep it level all the way round.
- 03Measure the neck: wrap the tape around the base of the neck, where it meets the shoulders — lower than where a collar usually sits.
- 04Write both numbers down in inches or centimeters. Measure twice; if the two readings differ, use the average.
- 05Compare chest girth with the chart. If your dog lands between two sizes, size down for a secure hold — the harness adjusts at several points.
Ready-Go Harness size chart
Chest girth picks the size; the neck range shows how far the neck opening adjusts. The product page always carries the current chart.
| Size | Chest girth | Neck |
|---|---|---|
| S | 19–25 in / 50–64 cm | 18–27 in / 45–68 cm |
| M | 24–31 in / 61–81 cm | 20–31 in / 52–80 cm |
| L | 28–38 in / 70–95 cm | 26–37 in / 66–93 cm |
Check the fit
Once the harness is on and adjusted, run through these checks before your first walk, and again every few weeks for growing puppies or dogs that change weight.
| Check | Good fit | Adjust if |
|---|---|---|
| Two-finger test | Two flat fingers slide under every strap | You can't fit two fingers (too tight) or can fit a whole hand (too loose) |
| Behind the front legs | Strap sits a hand's width behind the armpit | It rubs or presses into the armpit |
| Chest plate | Sits centered on the breastbone | It slides to one side when your dog walks |
| Back-out test | The harness stays put if your dog stops and leans back | It slides forward over the shoulders |
Small, medium and large dogs
Breed is a rough guide at best — two dogs of the same breed can be a size apart, so always go by the tape. As a starting point, small dogs usually fall in S, most medium dogs in M, and large, deep-chested dogs in L. If your dog is at the very top or bottom of a range, re-check the fit after a week of walks once the straps have settled.
Gear mentioned in this guide
Questions owners ask
- What if my dog is between harness sizes?
- Size down. The Ready-Go Harness adjusts at several points, and the smaller size gives a more secure hold. If you're unsure, email help@gentlewuff.com with both measurements — exchanges are free within 30 days if the fit isn't right.
- Should I measure over my dog's fur?
- Yes. Measure against the coat with the tape snug but not compressing it. For very fluffy dogs, press the tape lightly so it reads the body, not the fluff.
- How tight should a dog harness be?
- You should be able to slide two flat fingers under every strap. Any looser and your dog may be able to back out; any tighter and it can rub.
- How often should I re-measure a puppy?
- Check the fit every couple of weeks while your puppy is growing, and re-measure whenever the two-finger test gets tight.