How to Choose the Right Cat Litter Box Size
Quick answer. Disclosure: bestcatgear.com participates in the Amazon Services LLC Associates Program and may earn a commission from qualifying purchases, at no extra cost to you. Check the current price on Amazon. Measure your cat from its nose to the tip of its tail. Multiply that length by 1.5. Choose a box whose length, as measured on the box, is at least that number. The AAHA/AAFP Feline Life Stage Guidelines give this rule, and they note that most manufactured boxes are not large enough. Check the box’s stated size, not only the title, because some listings give two different sizes.
The person typing “how to choose a cat litter box size” wants a number to check before buying, and a way to read a listing’s size. Many people buy a box that looks large enough on the page and find it is short once they measure. This guide gives the rule, a worked example, two listings that show how sizes are stated, and the steps to check before you pay. It does not name a best box, and it does not say which size suits a particular cat’s health.
Step 1: measure your cat
Measure from the nose to the tip of the tail. The AAHA/AAFP guideline uses this measurement. Measure a calm cat against a tape or a ruler, and write the number down.
Step 2: multiply by 1.5
The guideline says the box should be at least one and a half times the length of the cat, from nose to tip of the tail. The table shows the arithmetic. The cat lengths are examples, not measurements of a real cat.
| Cat length, nose to tip of tail (example) | Minimum box length (cat length x 1.5) |
|---|---|
| 16 inches | 24 inches |
| 18 inches | 27 inches |
| 20 inches | 30 inches |
Step 3: check the box’s stated size
Read the size as the listing states it, and check the details table as well as the bullets. The two may not agree. The Bartuke XXXL listing is an example. Its bullet says 28 x 20 x 18 inches. Its details table says 27.56 x 19.69 x 15.75 inches. The length differs by about 0.4 inch, and the height by 2.25 inches.
Work out the cat length each figure would suit:
- 28 inches (bullet) divided by 1.5 gives about 18.7 inches, so a cat up to about 18.7 inches nose to tip of tail.
- 27.56 inches (table) divided by 1.5 gives about 18.4 inches.
If your cat measures 18.5 inches, the bullet figure fits and the table figure does not. Measure the box yourself if the number matters.
The Arm & Hammer Large Sifting Litter Box listing says it follows the guideline of being 1.5 times longer than the cat. The parts of that listing we read do not give the box’s inside length in inches, so the claim cannot be checked against a number on the page.
Step 4: check the edges and the number of boxes
The AAHA/AAFP guideline says box edges should not be too high for a kitten or a senior cat to enter and leave easily. It also gives a rule of thumb of one box per cat plus one additional box. Neither listing named here states an edge height in the parts we read. The Bartuke listing includes a removable two-step stair, which the listing says suits cats of all ages.
Products named in this guide (optional)
You do not need a product to apply the rule. If you want to compare the two listings named above, both were opened on Amazon on 2026-10-17.
- Bartuke XXXL Stainless Steel Litter Box, enclosed. Stated size: 28 x 20 x 18 inches (bullet) and 27.56 x 19.69 x 15.75 inches (table). View on Amazon
- Arm & Hammer Large Sifting Litter Box. The listing says it is a sifting box, not a scoop, and that it follows the 1.5 times guideline. View on Amazon
When you do not need a new box
If the box you already use is at least 1.5 times your cat’s length and your cat uses it without trouble, you do not need a new box for this rule. If the box is smaller than the rule, the guideline says a larger storage container is likely to reach the right size.
Mistakes to avoid
- Choosing by the word “large” in a title. Check the stated number.
- Measuring to the base of the tail. The guideline measures to the tip.
- Taking a size from a bullet without checking the details table. The Bartuke listing gives two sizes.
Source
AAHA/AAFP Feline Life Stage Guidelines, “General Litter Box Considerations”, AAHA, published February 18, 2021. Opened 2026-10-17: AAHA General Litter Box Considerations. The guideline is described by its authors as a guideline only, not a standard of care.
Frequently asked questions
How long should a litter box be for a cat?
The AAHA/AAFP guideline says the box should be at least one and a half times the cat’s length, measured from nose to tip of the tail. For an 18-inch cat, that is 27 inches.
Does the rule count the tail?
Yes. The guideline measures from the nose to the tip of the tail.
Are most boxes large enough by this rule?
The guideline says most manufactured boxes are not large enough, and that larger storage containers are likely to reach the right size.
How many boxes does a home need?
The guideline’s rule of thumb is one box per cat plus one additional box.
Does the Bartuke box fit an 18-inch cat?
The bullet figure of 28 inches suits a cat up to about 18.7 inches. The table figure of 27.56 inches suits up to about 18.4 inches. Both fit an 18-inch cat under the rule.
