Free tool
Pet urn size calculator
Enter a weight, get the minimum internal capacity to plan for in both cubic centimetres and cubic inches. The rule behind it is an industry planning convention, and we say so.
Uses the one cubic inch per pound capacity convention attributed to the Cremation Association of North America, the same rule already published across our pet urn guidance. It is a planning convention, not a scientific standard.
Your capacity estimate will appear here
Enter a weight to see the minimum internal capacity to plan for. Nothing you type is sent anywhere or stored.
Evidence and method
Method
How this works
The whole model, in plain language. Nothing here is hidden behind a black box.
- One cubic inch of capacity per pound of healthy body weight
- That is the whole rule. In metric it works out at about 36.1 cm³ per kg, derived from the exact conversion rather than rounded separately, so the metric and imperial answers always agree.
- It deliberately overestimates, and that is the point
- Cremated remains occupy far less volume than the living animal. Sizing against pre-cremation weight builds slack into the estimate rather than risking an urn that turns out to be too small, which is a problem you would rather not discover at the worst possible moment.
- The extra room is our suggestion, not part of the rule
- We default to 20 percent because providers usually build in a little room and many families want space for a keepsake such as a collar tag. It is adjustable, and we always show the bare planning figure alongside it so you can see both.
- This is a planning convention, not a standard
- It is an industry rule of thumb, not a scientific finding and not a crematorium guarantee. The volume of ashes a cremation actually produces varies with the individual animal's bone density and body composition and with the crematorium's process. Treat the number as something to check an urn against.
- Use the healthy adult weight
- If your pet lost or gained a lot of weight through illness, their healthy adult weight is the better starting point. It is the figure the convention was built around.
Limits
What this cannot tell you
- The result is a capacity to plan for, not a prediction of how much ash there will be.
- Final Tail does not sell urns and holds no urn pricing, so this tool never quotes a price.
- Confirm the capacity you need with your provider before buying, particularly if you want room for a keepsake.
Sources
Where this comes from
Every source we used, what it supports and when we retrieved it. If one of these changes, this page is wrong and we want to know.
Cremation Association of North America
Cremation Association of North America
CANA is the recognised North American cremation industry body, and is the origin cited across the memorial industry for the one cubic inch of capacity per pound of body weight convention. The pet aftercare industry applies the same rule to animals by practice, not because of any finding about animals specifically. We record that honestly rather than implying a veterinary basis.
Retrieved 29 July 2026
Final Tail
Pet urn sizing guidance already published across the memorial pages
Final Tail already publishes this same convention on its Australian, UK and US pet urn, dog urn and cat urn pages, in both metric and imperial form. This calculator uses the identical rule, so the tool and the guidance pages can never contradict each other.
Retrieved 29 July 2026
Questions
Common questions
How much ash will my pet actually produce?
Nobody can tell you in advance, which is why this tool gives a capacity to plan for rather than a prediction of output. The volume depends on the individual animal's bone density and body composition and on the crematorium's process. The convention deliberately overestimates so the urn you choose has room.
Is one cubic inch per pound a scientific standard?
No. It is an industry planning convention, attributed to the Cremation Association of North America and extended to pets by the aftercare and memorial industry. We say so in the interface rather than letting the number look more authoritative than it is.
Should I measure internal or external urn dimensions?
Internal capacity, always. Urn makers describe capacity in different ways, and an urn's outside dimensions tell you nothing reliable about what fits inside. If a listing does not state internal capacity in cubic inches or cubic centimetres, ask.
What about a very small pet?
For a rabbit, guinea pig, bird or similar, the capacity needed is small enough that a keepsake vessel is often the practical choice rather than a standard urn. Ask the provider what they can supply at that size.
Do you sell urns?
No. Final Tail is a directory and information service. We hold no urn pricing and this tool never quotes a price.
Final Tail is an independent directory of pet cremation and aftercare providers across Australia. We collect provider details from public listings, provider websites and information shared with us. Services, availability and pricing may change, so please confirm directly with the provider before making arrangements.