How to Measure Your Small Dog for a Harness (Without Guessing)
If you've ever bought a harness online and watched it arrive too tight, too loose, or just plain wrong — you're not alone.
About 30% of online dog gear purchases get returned for size issues.
For small dogs, that number is even higher. Why? Because most size
charts give you one number (chest girth), and small dogs come in
shapes that one number can't capture.
A 12-pound Frenchie and a 12-pound Dachshund are the same weight.
They have completely different bodies. A harness sized by weight
alone will fit one and not the other.
I learned this the hard way when I noticed my parents' Frenchie Tibby
and my buddy's mini poodle ended up in wildly different harness
sizes despite both being "small dogs."
This guide walks you through the four measurements that actually
matter, how to take them correctly, and how to match them to a size
chart that won't lie to you.
──────────────────────────────────────────
The four measurements you actually need
Most websites ask for chest girth. That's not enough.
For a harness that actually fits a small dog, you need four numbers:
1. Chest girth — around the widest part of the chest, just behind
the front legs
2. Neck girth — around the base of the neck, where a collar would sit
3. Chest depth — from the top of the shoulders down to the bottom
of the chest
4. Back length — from the base of the neck to the base of the tail
The first two are what most charts ask for. The last two are what
separate "fits well" from "fits weirdly."
──────────────────────────────────────────
How to take each measurement (do this right)
You'll need a soft measuring tape — the kind tailors use. Not a
metal one. If you don't have one, a piece of string and a ruler work
fine; just measure the string after.
Have your dog standing on a flat surface. Not sitting. Not lying
down. Not being held. Standing.
If your dog won't stand still, you're going to need a second person,
some treats, or both.
Chest girth (the most important number)
Find the widest part of your dog's ribcage — usually just behind
the front legs. Wrap the tape around the chest, snug but not tight.
You should be able to slide two fingers under the tape.
Common mistake: measuring too far back. The widest part is right
behind the legs, not in the middle of the belly.
Neck girth
Wrap the tape around the base of the neck, where a flat collar would
naturally sit. Snug, not tight — two fingers should still slide
under.
Common mistake: measuring at the top of the neck (near the head).
The base, where the neck meets the shoulders, is what fits a harness.
Chest depth
This is the one most people skip. From the top of the shoulders,
measure straight down to the deepest point of the chest. For most
small dogs, this is somewhere between 4 and 8 inches.
Why it matters: a harness sized to your dog's chest girth might
still ride up awkwardly or bunch if the chest depth is wrong.
Barrel-chested breeds (Frenchies, Pugs, Bostons, English Bulldogs)
have deeper chests than their girth suggests.
Back length
From the base of the neck (where the collar sits) to the base of
the tail. This matters less for harnesses than it does for carriers
and apparel, but it's worth taking while you have the tape out.
Common mistake: measuring to the tip of the tail. The base of the
tail is where the spine ends, not where the fur ends.
──────────────────────────────────────────
When your dog measures between sizes
This is going to happen. Small dogs are rarely a clean fit on a
size chart.
The general rule: size up. A slightly loose harness can be
tightened with adjustment straps. A slightly tight harness can't
be made bigger.
Exceptions:
- Step-in harnesses: size down if between sizes. They have less
adjustment room.
- Front-clip "health" harnesses: size to chest girth and ignore
weight ranges entirely.
- Padded vest harnesses: size up. Padding compresses over time,
and a tight vest gets uncomfortable fast.
If your dog is borderline on multiple measurements — say, neck
fits a Small but chest fits a Medium — pick the harness with the
most adjustment points. A harness with adjustable straps at both
the neck AND belly will accommodate weird proportions better than
one with a single fixed strap.
──────────────────────────────────────────
Weight charts lie. Here's why.
If you've ever ordered a harness based solely on your dog's weight and ended up returning it, you're not alone. Weight is one of the easiest measurements for brands to advertise, but it's one of the least useful measurements for predicting fit.
You'll see size charts like:
XS: 5-10 lbs
S: 10-15 lbs
M: 15-20 lbs
Ignore these. Weight tells you almost nothing about whether a
harness will fit.
Two examples:
A 12-lb Chihuahua has a small chest girth, a narrow neck, and a
shallow chest. Most "XS" harnesses fit fine.
A 12-lb Frenchie has a wide chest girth, a thick neck, and a deep
barrel chest. Most "XS" harnesses will be too narrow across the
chest, even though the weight is "right."
Use the actual measurements. The weight chart is for marketing,
not for fit.
Tibby wears a Medium harness in most brands despite being considered a small dog. A Chihuahua with similar weight would often wear an XS.
──────────────────────────────────────────
Breed-specific notes
Some small breeds have known fit quirks. Here's what to watch for:
French Bulldogs and Pugs (and other brachycephalic breeds):
Wide chest, thick neck, deep chest depth, short back. Size by chest
girth. Look for "barrel-chested" or "brachycephalic-friendly"
harnesses.
Dachshunds:
Long back, narrow chest, short legs. Standard harnesses often
don't account for back length. Look for "Dachshund-specific" or
adjustable-length harnesses.
Chihuahuas and tiny breeds (under 8 lbs):
Tiny everything. Most "XS" harnesses are actually sized for 10-lb
dogs. Look for "XXS" or "toy breed" specifically. If your dog is
under 5 lbs, search for "teacup" or "Chihuahua" specifically.
Yorkies, Maltese, and other toy breeds with long coats:
Coat can add an inch or more to apparent measurements. Measure
against the skin if possible — part the fur and measure underneath.
Otherwise, size up.
Pomeranians:
Deceiving. The fluff makes them look bigger than they are. A fully
groomed Pom is often a size smaller than an ungroomed one. Measure
against the skin.
Mini Doodles, Cavaliers, Shih Tzus:
Average small-dog proportions. Standard sizing usually works.
Measure chest girth and go from there.
──────────────────────────────────────────
If your dog won't cooperate
Real talk: a lot of small dogs hate being measured. Strategies that
work:
1. Measure right after a meal — they're calmer and slower
2. Use treats as a distraction while a second person measures
3. Measure while they're standing for a different reason (food bowl,
treat at eye level)
4. If all else fails, measure them while they're sleeping. It's
not as accurate, but it's better than guessing.
If you absolutely can't get a good measurement, look for brands
with generous return policies. A 30-day return window means you
can order, try, and return if it doesn't fit.
If your dog is anything like Bruce, getting them to stand still for measurements can be... challenging. We've had the best luck with the classic "hold still for five seconds and earn a cookie" strategy.
──────────────────────────────────────────
Quick reference: small dog measurements at a glance
Most small dogs fall within these ranges. If yours is way outside
these, double-check your tape isn't twisted:
| Chest girth: | |
| - Toy breeds (under 8 lbs): | 11-14 inches |
| - Small breeds (8-15 lbs): | 14-18 inches |
| - Medium-small (15-25 lbs): | 18-24 inches |
| Neck girth: | |
| - Toy breeds (under 8 lbs): | 7-10 inches |
| - Small breeds (8-15 lbs): | 10-14 inches |
| - Medium-small (15-25 lbs): | 14-17 inches |
| Chest depth: | |
| - Most small breeds: | 4-7 inches |
| - Barrel-chested breeds: | add 1-2 inches |
| Back length: | |
| - Toy breeds (under 8 lbs): | 8-11 inches |
| - Small breeds (8-15 lbs): | 11-15 inches |
| - Dachshunds: | 12-20 inches (they're long) |
──────────────────────────────────────────
What to do once you have your numbers
Write them down. Save them in your phone notes. You'll use them
every time you buy a harness, carrier, coat, or anything else for
your dog.
When you find a harness you like, compare the brand's size chart
to YOUR measurements — not to the weight or breed listed. If a
brand only shows weight ranges, email them and ask for actual
measurements before buying. A brand that won't share their size
chart isn't worth your money.
──────────────────────────────────────────
What we look for in sizing (and how Wiggle handles it)
When we evaluate a harness for Wiggle, here's what we check:
- Does the brand publish actual measurements (not just weight)?
- Are there multiple size variants for similar weight ranges?
- Do they have specific guidance for barrel-chested or long-bodied
breeds?
- Do they offer easy returns if the fit is wrong?
If a harness fails any of these checks, it doesn't make it onto
Wiggle. We'd rather carry fewer options that fit well than dozens
that don't.
──────────────────────────────────────────
Frequently Asked Questions
How tight should a dog harness be?
A properly fitted harness should be snug but not restrictive. You should be able to slide two fingers between the harness and your dog's body.
Should I size up if my dog is between harness sizes?
In most cases, yes. A slightly loose harness can usually be adjusted, while a tight harness cannot.
Can I use my dog's weight to choose a harness size?
Weight can be a starting point, but chest girth, neck girth, and body shape are far more accurate indicators.
How often should I measure my dog?
Adult dogs usually only need to be measured once a year unless they gain or lose weight. Puppies should be remeasured every 2-3 months.
──────────────────────────────────────────
One more thing
If you do this once and write down your dog's measurements, you
don't have to do it again for a year. Small dogs are pretty
size-stable past puppyhood. Save the numbers, save yourself the hassle.
And if your dog is still growing — most small breeds are full-grown
by 9-12 months — re-measure every 2-3 months until they hit their
adult size.
Tibby, my parents' Frenchie, has been the same
size for four years. Bruce is still putting on chest width and is only 13 months old. Every dog's different. The numbers are what matter.
— The Wiggle team
