The Edit — Pets
ThunderShirt: The 80% and 89% Claims Against the Ratings
Thundershirt publishes 2 improvement figures: 80% on its own site and 89% on Amazon. Its 3 most-reviewed sizes rate 4.2 to 4.3 across 77,477 ratings, and owners split more sharply than either figure suggests.
This guide is research-led: we have not handled these units ourselves. If you buy through our links we may earn a commission — it never changes a pick.Research-led, nothing handled. We may earn from links; it never changes a pick. How we choose
This is an evidence profile: the published specification and the maker’s own claims, read against what owners consistently report across 3 size listings on Amazon. The sizes are ranked highest rating first, then most ratings, which puts the small size ahead of the medium, whose sample is twice as large. No ThunderShirt was fitted to a dog for this page.
ThunderShirt for Dogs Calming Anxiety Vest, Small
Good fit A small dog that fits the chart by chest girth
Not for Your dog sits between sizes on the chart
ThunderShirt for Dogs Calming Anxiety Vest, Medium
Good fit A mid-sized dog, measured at the chest
Not for Your dog will not stand still to be fastened
ThunderShirt for Dogs Calming Anxiety Vest, Large
Good fit Storms rather than separation are the trigger
Not for A dog that resists being handled around the chest
80% and 89% are owner-reported figures, not trial results
Thundershirt’s product page says 80% of users see improvement in their dog’s anxiety, citing a customer survey. The medium Amazon listing says 89% of pet parents reported improvement in stress-related behaviours, marked with an asterisk.
Both figures come from owners describing their own dogs, and neither page describes a control group. A survey of buyers can overstate a result, because owners who saw no change may be less likely to reply. The figures show that many owners are satisfied. They do not show how much of the calm came from the wrap.
Many dogs calm down; some do not change at all
Owners describe 2 outcomes. Many report a dog that stops shaking during storms. A consistent minority report no change at all, and some say the wrap was hard to fasten on a frightened dog.
The 3 most-reviewed size listings rate 4.2 to 4.3, and that split is why: it works well for some dogs and not at all for others.
ThunderShirt for Dogs Calming Anxiety Vest, Medium
4.2 across 43,020 ratings, the most-reviewed calming wrap in Amazon's search results on 16 September 2026, sized by Thundershirt for dogs of 26 to 40 lb.
Current price shown on Amazon. We may earn a commission.
| Chest | 25 in |
|---|---|
| Weight range | 26–40 lb (maker's chart) |
| Weight of wrap | 8.4 oz |
43,020 ratings, and this is the size listing that carries the 89% claim. Owners describe dogs taking to it easily, and several name separation anxiety specifically.
The complaint that recurs is a dog that showed no change at all, and some owners find it hard to fasten. The listing gives a 25-inch chest and a wrap weight of 8.4 oz, and Thundershirt’s own chart sizes the medium for dogs of 26 to 40 lb.
Buy it if
- A mid-sized dog, measured at the chest
- You want the largest sample of owner reports
Don't buy it if
- Your dog will not stand still to be fastened
Sizing by chest girth decides whether pressure is even
A compression wrap works by constant, even pressure, which Thundershirt compares to swaddling an infant. A wrap that is too loose applies none, and one that is too tight is simply uncomfortable. The medium listing, for example, gives a 25-inch chest.
Thundershirt’s own chart sizes by weight alone, from under 8 lb for the XXS to over 110 lb for the XXL, and it advises sizing down when a dog sits at the edge of a weight range. The Amazon listings add a chest size, and a deep-chested dog can measure into a different size than its weight suggests, so check both. The same measuring habit applies to a harness, and how a dog harness should fit sets out the checks.
ThunderShirt for Dogs Calming Anxiety Vest, Small
4.3 across 21,495 ratings, a tenth above the other sizes, with owners describing it as easy to put on.
Current price shown on Amazon. We may earn a commission.
| Size | Small |
|---|---|
| Mechanism | Constant torso pressure |
| Evidence | 21,495 ratings |
4.3 across 21,495 ratings makes the small the highest-rated listing, so it ranks first on half the medium’s ratings. Owners call it easy to get on and off and say their dogs relax in it. Thundershirt sizes the small for dogs of 15 to 25 lb.
Some owners call it well worth the money and others call it overpriced, and a few found it ran off the size chart. A tenth of a point across 2 samples this size is a small gap, and it is not a reason to choose a size that does not fit.
Buy it if
- A small dog that fits the chart by chest girth
- You want the highest-rated listing of the 3
Don't buy it if
- Your dog sits between sizes on the chart
For storms and fireworks, practise the fit first
Storms are where owners of the large ThunderShirt praise it most, describing dogs that stop hiding and shaking. It is also where they most often report the wrap failing, or being impossible to fasten on a panicking dog.
Both points lead to the same practice: fit the wrap on calm days first, so it is familiar and quick to fasten before a storm arrives. The wider plan for fireworks nights matters more than the wrap alone: a quiet room, masking sound and a long-lasting chew.
ThunderShirt for Dogs Calming Anxiety Vest, Large
4.2 across 12,962 ratings, where the storm reports are strongest and the difficulty of fastening it comes up most.
Current price shown on Amazon. We may earn a commission.
| Size | Large |
|---|---|
| Evidence | 12,962 ratings |
| Watch | Fastening difficulty reported |
4.2 across 12,962 ratings, where storm-specific praise is most common. It is also where owners most often say the wrap did not work, or was close to impossible to put on.
For a large dog, practise the fastening on a calm afternoon. A fit that is easy on a relaxed dog becomes a struggle once the dog is frightened.
Buy it if
- Storms rather than separation are the trigger
- A large dog that tolerates a coat
Don't buy it if
- A dog that resists being handled around the chest
Cheaper wraps, and when to see a vet
The nearest alternative, the Mellow Shirt calming wrap, rated 3.9 across 10,519 ratings when its medium listing was read on 11 October 2026. Owners report that its sizes run large and that it does not suit dogs around 10 lb. Unbranded anxiety vests in the same search results have far fewer ratings.
No wrap calms every dog, and nothing in owner reports predicts which dogs respond. A dog whose fear causes injury or escape attempts needs a vet, and a wrap is not a substitute.
Prices, savings and deal badges are Amazon's own, read from Amazon within the last hour. Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon.com at the time of purchase will apply to the purchase of this product.
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ThunderShirt for Dogs Calming Anxiety Vest, Small