Automatic Litter Box for Large Cats: Weight Limits and Sizes

The highest published cat weight limits belong to the Neakasa M1 Plus and M1 Lite Plus, at “around 33 lbs”. Next is Whisker’s Litter-Robot 5, which has a hard 30 lb limit, the widest published entryway in our data (15.75 in) and the tallest published interior (17.5 in). The Litter-Robot 4 and PetSafe SmartSpin both list 25 lb. The PETKIT Purobot Max 3 lists 22 lb and the Litter-Robot EVO 19 lb. PetSafe does not publish a weight limit for the Crystal Smart.

Weight limits and sizes by model

All figures are the makers’ own, checked 2026-11-02. A dash means the maker does not publish that figure.

The Whisker footprints are printed as “22” x 27”” without axis labels. The PetSafe Crystal Smart dimensions are also unlabeled. PETKIT also lists a “Cylinder Space” of 76 L for the Purobot Max 3.

What “entry size” means where it is published

Makers measure the opening in different ways, so the numbers don’t line up one-to-one:

• Whisker gives a width × height for the “Entryway”: 15.75 × 15.75 in on the Litter-Robot 4 and 5, and 14.85 × 14.85 in on the EVO. It also gives an interior height for each globe in its FAQs.
• PETKIT gives an “Entry Size” of 10.51 × 10.74 in (267 × 273 mm) in its comparison table. It also gives a separate “Entrance Height” of 8.03 in (204 mm). PETKIT does not label it, but this looks like how high the opening sits, not how big it is. PETKIT adds: “Cats do vary in length and shape. Check the entry dimensions to guarantee a comfortable fit for your cat.”
• Neakasa lists “Entry Height 13.86” (Easy Access)” and does not say what is measured. Because the M1 is open-top, there is no doorway to fit through.
• PetSafe gives no opening size for the SmartSpin. The page only says the entry is “just 12 in. from the ground.”

To check fit, measure your cat and compare against the entry and interior figures.

Models with the highest stated limits

Neakasa M1 Plus and M1 Lite Plus: around 33 lb. Neakasa’s FAQ says the open-top design “almost does not have a weight limit. But we recommend it for cats weighing 2.2- around 33 lbs for the best comfort.” It names “Maine Coons and Ragdolls” as breeds the open top is meant for. Prices are $549.99 list / $399.99 sale (M1 Plus) and $499.99 / $379.99 (M1 Lite Plus) as of 2026-11-02. Details are on the Neakasa M1 page.

Whisker Litter-Robot 5: 30 lb. Whisker says it suits “cats that weigh 3-30 lbs, including extra large breeds like Maine Coons or Norwegian Forest cats.” It adds that “with an entryway width of 15.75” and an interior height of 17.5”, almost any domestic cat can fit comfortably inside the globe.” The list price is $799 with no sale as of 2026-11-02.

Whisker Litter-Robot 4 and PetSafe SmartSpin: 25 lb. The Litter-Robot 4 has the same entryway as the 5 and a 16.5 in interior height ($699, no sale). PetSafe says the SmartSpin is “for cats up to 25 lb” ($399.99). See the Litter-Robot 4 page.

The Litter-Robot EVO is the compact one. Whisker lists it at 3–19 lb with a 14.5 in interior. Whisker itself says: “If you have an especially large or tall cat, consider Litter-Robot 5 or Litter-Robot 4.”

Weight limits work in both directions

Several of these boxes use weight sensing to detect visits. That is why each one lists a minimum weight as well as a maximum: 3 lb for Whisker, 2.2 lb for Neakasa and 3.3 lb for PETKIT. A published maximum is the maker’s design figure, not a promise that every cat of that weight will be comfortable.

The Cornell Feline Health Center notes that “Overweight and large cats need bigger boxes.” It also says “Most cats prefer an uncovered box that lets odors escape and allows a 360-degree view of their surroundings.” The trade-offs are covered in open-top vs. enclosed. If a large cat strains, struggles to get in or changes its litter habits, check with your veterinarian.

Bottom line

If weight is your main filter, the Neakasa M1 models list the highest limit (“around 33 lb”) and the Litter-Robot 5 lists 30 lb. Whisker also publishes the widest entryway and tallest interior in our data. For each model, compare the entry size, interior height and outer size against your cat and your space, not just the weight figure. The comparison table puts all of these side by side.