When you’re grieving, the last thing you want is to worry about math. Yet many families find themselves asking the same urgent question: “What size urn do I need?” Understanding urn capacity, how cubic inches work, and how adult, child, and pet urns are sized can make this part of the process much gentler.
This guide walks you through a simple urn capacity guide for adults, children, and pets, explains the common weight-to-cubic-inches rule, and shows you how to read product specifications when you’re shopping online. We’ll also talk about keepsake urns, sharing urns, companion urns, and practical tips like leaving room for paperwork or small mementos inside the urn.
Understanding urn capacity and cubic inches
Urns are usually described by capacity, not just by height or width. Capacity is almost always listed in cubic inches. That number tells you the approximate volume of space inside the urn where the cremated remains can rest.
Think of cubic inches the way you’d think of the size of a box. If you measured the inside of a container as 8 inches tall, 6 inches wide, and 4 inches deep, you’d multiply those numbers (8 × 6 × 4 = 192) to get 192 cubic inches of space.
When you’re choosing urn size, that capacity number matters more than whether the urn “looks big enough” in a photo. Two urns can be the same height but have very different capacities if one is much wider or deeper than the other.
That’s why, when you’re comparing cremation urns for ashes, it’s helpful to focus on phrases like “Capacity: 200 cubic inches” or “Volume: 400 cubic inches (companion urn)” rather than just the outside measurements.
The weight-to-cubic-inches rule: a simple sizing shortcut
The most common rule of thumb families hear in any urn capacity guide is the weight-to-cubic-inches rule:
Each pound of body weight before cremation needs about one cubic inch of urn capacity.
In other words, a person who weighed 150 pounds will usually need an urn that holds at least 150 cubic inches. Someone who weighed 220 pounds will usually need an urn that holds around 220 cubic inches or more.
This is not an exact science—bone structure, cremation equipment, and other factors can affect the final volume—but it is a very useful shortcut when you’re asking yourself what size urn do I need.
Because you can’t know the exact volume ahead of time, it’s wise to round up rather than choosing an urn that’s right on the edge. When in doubt, choosing a slightly larger adult cremation urn size is safer and more flexible than choosing one that may be too small.
Adult cremation urn size and “oversized” options
Most standard adult cremation urns for ashes are designed for a typical adult. You’ll often see capacities in the 180–220 cubic inch range, with 200 cubic inches being a standard size.
Here’s how that connects to everyday questions:
- If your loved one weighed up to about 180–200 pounds, a standard adult urn of around 200 cubic inches is usually appropriate.
- If your loved one weighed more than 200–220 pounds, you may want to look for an “extra-large” or oversized urn with a capacity of 230–300+ cubic inches.
- If your loved one was very tall or had a large frame, it’s reasonable to choose a larger urn even if the scale weight doesn’t seem unusually high.
An urn can be too small, but it can’t really be “too big” in a functional sense. If the urn has extra room inside, the ashes will still rest securely; you simply won’t fill the entire interior space. For many families, that extra space is welcome, because it allows room for small mementos as well.
If you prefer to shop by specific style, you might look at a classic design like our Classic Bronze Three Band Adult Cremation Urn or other full-size urns in the adult collection.
Child and infant urn size: gentle guidelines for small ones
Choosing a child urn size or infant urn size can feel especially tender. The same weight-to-cubic-inches rule applies here, but the numbers are smaller.
In general:
- Infant urns often range from about 10 to 60 cubic inches, depending on age and size.
- Child urns commonly range from around 60 to 120+ cubic inches.
If you know the child’s approximate weight, use the one pound ≈ one cubic inch guideline and round up. For example:
- A child who weighed 40 pounds before cremation will usually need an urn that holds at least 40 cubic inches, and many families choose something in the 50–70 cubic inch range to feel comfortable.
- A child who weighed 80–90 pounds may be better served by a small adult-sized urn in the 100–120 cubic inch range.
If you’re unsure, you can always ask the funeral home or crematory for advice, or choose a slightly larger urn and, if there is extra space, place a tiny toy, drawing, or letter inside along with the ashes.
Some families also choose a full-size urn and then add a smaller heart keepsake urn so siblings or grandparents can keep a small portion close.
Pet urn size: using the same rule for animals
Families often ask for a pet urn size chart for dogs, cats, and other animals. While different brands may publish slightly different charts, they are almost all using the same basic rule:
One pound of your pet’s weight needs about one cubic inch of capacity.
Some simple examples:
- A cat who weighed 10 pounds will usually fit comfortably in a pet urn of at least 10–15 cubic inches.
- A small dog who weighed 25 pounds will typically need a pet urn of 25–40 cubic inches.
- A large dog who weighed 70 pounds will generally need a pet urn of 70–100 cubic inches or more.
Because many families see their animals as true family members, you’ll sometimes see pet urns for ashes offered in the same capacities as human urns. It’s perfectly appropriate to choose a full-size adult urn for a large dog or a symbolic design that simply feels right, as long as the cubic inches needed for an urn match or exceed your pet’s weight.
For example, a design like our Raku Paw Print Jar Pet Cremation Urn is sized to comfortably fit many medium and large pets.
Keepsake and sharing urns: very small capacities by design
Not every urn is meant to hold all of a person’s or pet’s ashes. That’s where keepsake urns and sharing urns come in.
A keepsake urn is usually a small urn that holds just a portion of the remains. Keepsake urn capacity can be as little as 1–3 cubic inches, or sometimes up to 20–50 cubic inches, depending on the style.
A sharing urn is slightly larger and is meant for situations where ashes are divided between several family members. Sharing urn capacity is often in the 20–100 cubic inch range.
There’s also cremation jewelry, which holds an even smaller portion—typically less than a teaspoon of ashes. By design, these pieces are not intended to hold everything, but they can be a meaningful way to keep a loved one close while the majority of the ashes rest in a larger urn or are scattered.
If you plan to divide ashes among several people, you might use one full-size adult urn or companion urn as the primary resting place and choose multiple keepsake urns or jewelry pieces so each person can carry a small portion.
Companion urns: capacity for two people
A companion urn is designed to hold the ashes of two adults together, either in a single shared chamber or in two separate compartments.
Typical companion urn capacity is around 350–400+ cubic inches, with many designs centered around 400 cubic inches. That’s essentially two standard adult urns combined into one memorial piece.
Families often choose companion urns when:
- A couple planned ahead and wanted their ashes kept together.
- One partner has died and the other expects to be cremated in the future; the urn can hold the first person’s ashes now and the second’s later.
- Two close relatives—such as siblings, a parent and child, or lifelong friends—are being memorialized together.
Companion urns can also be a good solution for an oversized urn need, such as when one adult’s ashes require a much larger capacity and the family also wants space for mementos.
Urn size for scattering: how much space do you need?
If you plan a scattering ceremony, you might choose a dedicated scattering urn or scattering tube instead of (or in addition to) a permanent display urn.
For full scattering, you still want a container large enough to hold the entire amount of ashes. In that case, you can use the same what size urn do I need rule: one cubic inch per pound of body weight, rounded up.
If you are scattering only part of the ashes and keeping the rest in an urn, choose a scattering container that matches the portion you plan to scatter and keep the remainder in an appropriate adult urn, child urn, infant urn, pet urn, or keepsake urns for family members.
How to read urn specifications when shopping online
Online shopping can raise a lot of cremation urn shopping tips and online urn size questions, because every product page looks a little different. A few details are especially helpful:
- Look specifically for capacity or volume listed in cubic inches.
- Don’t rely only on the height of the urn; a tall, narrow urn may hold less than a shorter, wider one.
- Look for phrases like “adult urn,” “child urn,” “infant urn,” “pet urn,” “companion urn,” “keepsake urn,” or “sharing urn” in the description and match that to your needs.
- If the listing mentions that the urn fits a standard plastic ash container from the crematory, that’s a sign it’s designed with practical sizing in mind.
If a product page doesn’t clearly list capacity, it’s reasonable to pause and contact customer support before buying. Clear, transparent urn capacity information is a sign that a seller understands what families actually need.
Leaving room in the urn for paperwork and mementos
Many families like the idea of leaving room in an urn for mementos—a small folded letter, a lock of hair, a wedding ring, dried flowers from the service, or a favorite photo—rather than filling it completely to the brim.
You might also want to include:
- The small paperwork envelope from the crematory.
- A copy of a favorite poem or prayer.
- A child’s drawing or handwritten note.
If you know you’ll want to tuck small items inside, simply choose an urn with extra capacity beyond the minimum needed for the ashes. For example, if the weight-to-cubic-inches rule suggests 180 cubic inches, you might choose a 200–225 cubic inch urn instead to give yourself room and peace of mind.
When you’re still unsure what size urn to choose
Even with all of these guidelines, it’s completely normal to feel unsure. Grief makes decisions harder, and you may worry about “getting it wrong” when selecting the right urn for your loved one.
A few reassurances:
- If you follow the one pound ≈ one cubic inch rule and round up, you are very unlikely to choose an urn that’s too small.
- Choosing a slightly larger adult cremation urn size, child urn size, infant urn size, or pet urn size is usually the safer and more flexible choice.
- If you receive the ashes before buying an urn, you can ask the funeral home or crematory how many cubic inches they recommend based on what they see.
- If an urn does turn out to be too small, families can use a keepsake urn or sharing urn for the small amount that doesn’t fit, or scatter that portion in a special place.
Most of all, remember that the love, memories, and stories you carry are much bigger than any number of cubic inches. The urn is a vessel for ashes, but it’s also a symbol of everything your loved one meant to you. If the design feels right and the capacity is safely large enough, you can trust that you’ve made a thoughtful, caring choice.
