Will your pet's ashes fit inside a memorial stone?
Cremated remains usually weigh about 3-5% of body weight[1], and they take up more room than most people expect. Enter your pet's weight to get the volume, then compare it with the compartment in the stone you like.
- Volume in cubic inches and millilitres
- Sharing and keepsake portions worked out
- Checks a stone's cavity before you buy
Urn size calculator
Enter your pet's healthy adult weight. We size the urn using the industry rule of 1 cubic inch per pound, plus 10% room to spare.
Recommended urn size
55 cu in (901 mL)
Look for: Medium (up to 60 cu in)
| Total ashes (by volume) | 50 cu in (819 mL) |
|---|---|
| Expected ash weight | 1.5 lb–2.5 lb |
| Urn with 10% margin | 55 cu in (901 mL) |
Standard sizes: small up to 20, medium up to 60, large up to 120 and extra large 200+ cubic inches. If you're between sizes, choose the larger one.
Source: Embrace Pet Insurance - Bury or Cremate Your Dog? Costs, Pros & Cons; Our estimate. 1 cu in per lb is an industry rule of thumb
Next step: Find urns and prices near you →
Using the calculator
How to size your pet's ashes in under a minute
Type your pet's healthy adult weight in pounds or kilograms. If you're sharing the ashes, set how many people will have a portion, and tick keepsakes if each person wants a keepsake urn of about 3 cubic inches. The result shows the total volume, the standard urn size that matches and how much each share would be.
On this site, most people use it for one reason: to check whether a memorial stone with a hidden compartment can hold all the ashes, or only part. Makers list cavity sizes in cubic inches or millilitres, so you can compare the two numbers directly.
The maths, openly
How the calculator turns weight into volume
The industry rule of thumb is one cubic inch of urn space for every pound of healthy body weight. The calculator adds a 10% margin, because ashes are returned in a bag that doesn't pack perfectly and it's frustrating when the last inch won't close. The rule is generous on purpose: ashes by weight are only around 3-5% of body weight[1], but they're bulky. The weight side comes from a published study of 100 cremations that found remains averaged about 3.5% of adult body weight, a benchmark pet crematories adapt. By our calculation, a 12 lb cat needs about 12 cubic inches and a 70 lb dog about 70[2], while a median-weight giant-breed dog of about 108 lb would return roughly 3.8 lb of ashes and need around 108 cubic inches[3].
| Size | Volume | Typical pet weight |
|---|---|---|
| Small | Up to 20 cu in | Up to about 18 lb: most cats, rabbits, small dogs |
| Medium | Up to 60 cu in | Up to about 54 lb |
| Large | Up to 120 cu in | Up to about 109 lb |
| Extra large | 200+ cu in (used up to 220) | About 110 to 200 lb: giant breeds, or two pets together |
| Large-animal urn, chest or several urns | Over 220 cu in | Over about 200 lb |
Memorial stones with compartments vary much more than urns. Many garden rocks hold a keepsake portion of 3 to 10 cubic inches; larger hollow markers often hold 20 to 60. Very few hold enough for a giant breed, which is why the sharing option matters on this site.
An example
Worked example: a 70 lb Labrador and a hollow granite marker
Bramble weighed 70 lb. The calculator gives 70 cubic inches plus a 10% margin, so about 77 cubic inches (roughly 1,260 mL), which sits in the large urn band. His family has chosen a hollow granite marker with a 40-cubic-inch sealed cavity.
- The marker holds about half of Bramble's ashes, not all of them.
- Setting sharing to two gives two shares of 35 cubic inches and a recommended urn of about 39 cubic inches each with the margin, so one share just fits the stone.
- The other half goes into a medium urn indoors, or is buried beneath the marker in a biodegradable bag.
Knowing this before ordering meant the family could choose between a larger stone and a split, rather than finding out when the ashes wouldn't fit. For context, US cremation for a pet of 51 to 70 lb is commonly listed at communal $50-100; private $200-300[4], so the ashes and stone are often the second big decision after the cremation itself.
Free tool
Urn size calculator
Find the urn volume you need from your pet's weight, plus keepsake and sharing options.
If you'll bury some
Burying ashes under the stone instead
Burying ashes beneath a marker is simple, and the volume tells you how big a hole to dig: 77 cubic inches is about the size of a large coffee can. Use a biodegradable urn or bag if you want the ashes to return to the soil, or a sealed container if you might move and want to take them.
Plants don't love raw ashes, which are very alkaline and salty. If you'd like to plant something beside the stone, gardening advice is to mix ashes with compost and let it rest 90–120 days[5] before planting, or bury them a little away from roots. The memorial tree finder suggests trees that suit your climate, and our guide to placing and maintaining a garden stone covers setting it over a burial. In the US, contact 811 before digging, even for a shallow hole; the service is free.
What it can't tell you
Where the estimate can differ from your pet's real ashes
- Dense-boned and giant breeds can return more ash than the rule suggests; very lean or elderly pets sometimes less.
- Cremation method and how finely the remains are processed change the volume slightly.
- Very small pets, like hamsters, birds or fish, may return only a teaspoon or so. Almost any keepsake compartment will do.
- A stone's stated cavity may not all be usable if the ashes stay in their inner bag.
If your pet is already cremated, the most accurate figure is the ashes themselves. Ask the cremation provider for the returned volume, or measure the container they came in. Cold climates bring one more concern: water in a poorly sealed cavity can freeze. Our cold-weather notes explain how to keep a compartment dry. Our local pages note which areas see hard freezes.
Next steps
Choosing a stone once you know the volume
Take your volume and compare stones that hold ashes with other options. If the wording is next, check it fits with the memorial stone planner. Or send us the number and your pet's name, and we'll find stones with a compartment that fits. Urns are the biggest single slice of the memorial market, generating 40%+[6] of pet memorial product revenue in one report, so there's plenty of choice if you decide to keep some ashes indoors too. Our post on moving house with a pet grave explains why a stone with a compartment is easy to take with you, and the live poll results show how other readers split or kept ashes.
Will your pet's ashes be with the stone?
Tap an answer to vote and see how others answered. Anonymous.
Reader polls
What would you choose?
Vote anonymously and see how other readers answered. The results are live counts from people who visit this site, so they show real opinions, not a scientific sample.
Will your pet's ashes be with the stone?
Tap an answer to vote and see how others answered. Anonymous.
If you moved house, what would happen to the memorial?
Tap an answer to vote and see how others answered. Anonymous.
Where are (or will be) your pet's ashes?
Tap an answer to vote and see how others answered. Anonymous.
Free tools to help you plan
Urn size calculator
Find the urn volume you need from your pet's weight, plus keepsake and sharing options.
Memorial stone planner
Plan size, material and engraving length so your wording fits the stone.
Memorial tree finder
Pick a tree for a planting urn that suits your climate, space and pet.
Questions people ask
How big a stone compartment do I need for a cat's ashes?
Most cats weigh 8 to 12 lb, so the calculator gives about 9 to 13 cubic inches with the margin. Many hollow garden stones and markers hold that comfortably. Small garden rocks with a keepsake cavity of 3 to 5 cubic inches will only take a portion.
Can all of a large dog's ashes go inside a memorial stone?
Sometimes, but only in larger hollow markers or purpose-built urn stones. A 90 lb dog needs about 100 cubic inches, which is more than most garden rocks hold. Many families place a portion inside the stone and keep the rest in an urn, or bury the rest beneath it.
Is it OK to divide my pet's ashes between a stone and an urn?
Yes, and it's common. Dividing lets the stone mark a place in the garden while part of your pet stays indoors or with other family members. Pour over a tray, use a spoon rather than shaking the bag, and wear a mask if you're sensitive to dust.
What does 1 cubic inch per pound actually mean?
It's the urn industry's shorthand: a 50 lb dog's ashes need roughly a 50-cubic-inch container. It isn't a physical law, just a reliable, slightly generous guide. The 10% margin the calculator adds covers bagging and slight variations between pets.
Sources and our estimates
- [1] Embrace notes cremated remains typically weigh about 3-5% of the pet's original body weight. Embrace Pet Insurance - Bury or Cremate Your Dog? Costs, Pros & Cons, 2025.
- [2] Using the industry rule of thumb of 1 cubic inch of urn space per pound of body weight, a 12 lb cat needs an urn of about 12 cubic inches; a 70 lb dog needs about 70 cubic inches. Our estimate: urn cu in = body weight lb x 1 (industry rule of thumb, not a measured value). How we calculate.
- [3] A median-weight giant-breed dog (48.8 kg / 108 lb) would be expected to return about 1.71 kg (3.8 lb) of cremated remains, needing an urn of about 108 cubic inches. Our estimate: 48.8 kg x 3.5% x 2.2046 lb/kg; urn = 108 lb x 1 cu in/lb. How we calculate.
- [4] CareCredit lists US communal cremation at $50-$100 and private at $200-$300 for 51-70 lb pets. CareCredit (Synchrony) - How Much Does Pet Cremation Cost? (Sept 2023), 2023.
- [5] Gardening Know How advises letting an ash/soil-amendment mixture sit for at least 90 to 120 days before planting. Gardening Know How — Planting With Cremains: Is There a Safe Way to Bury Ashes, 2024.
- [6] Pet urns generated over 40% of pet memorial product revenue in 2023. DataHorizzon Research — Pet Memorials Market report page, 2023.
Find a stone with the right-size compartment
Tell us what you need and where you are. We'll reply by email with clear options and prices so you can decide in your own time.