If you're reading this, chances are you've just received your loved one's ashes, or you're about to, and this is one of the first practical questions you're trying to answer.

It's a good question. And most sites answer it with a formula and leave you to figure out the rest.

This guide explains exactly what you need to know, in plain language, with New Zealand measurements throughout. By the end, you'll know the right size, why the standard advice exists, and what to do if your situation is a little more complicated.

The Sizing Rule

For every kilogram of body weight, cremated remains take up roughly 2.2 cubic inches of space.

So if your loved one weighed 70kg, the remains will be around 154 cubic inches in volume, which is approximately 2.5 litres.

If it helps to think in the older measure: one pound of body weight equals roughly one cubic inch. Same rule, different numbers.

Most standard adult urns hold 200 cubic inches, which is about 3.3 litres. A standard urn will comfortably fit the remains of most New Zealand adults.

Why You Should Always Go Slightly Larger Than the Calculation Suggests

You'll see this advice everywhere. But almost nobody explains the reason behind it.

When a crematorium returns ashes, they don't come loose. They come in a sealed plastic bag inside a temporary container. That bag doesn't compress flat. It takes up real space inside the urn, beyond what the weight calculation accounts for. Typically an extra 10 to 15 percent of capacity.

So a person who weighed 70kg might need 154 cubic inches based on the formula. With the bag factored in, the practical requirement is closer to 170 cubic inches. A 200 cubic inch urn handles this easily. A 150 cubic inch urn may not close properly.

An urn that's too big can hold a small sachet inside. An urn that's too small can't.

That's why the standard 200 cubic inch urn exists as the industry benchmark, not just because it fits average remains, but because it fits the bag and still has room.

A Quick Reference for Common Weights

This visual replaces the table below for web use. Keep the table as a text fallback for accessibility.

One important note: for anyone who weighed over 110kg, a standard adult urn won't be sufficient.

Look for an urn listed at 220 cubic inches or above, or contact us directly and we'll point you to the right option.

Our standard adult urns are mostly 3.4 litres (approximately 207 cubic inches), which comfortably fits remains up to and including 90kg once the sealed bag is accounted for.

We have a small selection of extra large cremation urns for people who weighed over 94kg.

If You're Not Sure of the Weight

This is more common than people expect, especially if the death was sudden or if family members are handling arrangements from a distance.

A few ways to find out:

The crematorium will have recorded the weight before cremation. Call and ask. The person's GP or the hospital where they passed may have it on file. A reasonable estimate is fine. If you're unsure, round up and choose the next size larger.

You don't need an exact number. The formula gives an approximation, and a small buffer is always the sensible choice.

When You Want to Share the Ashes Among Family

This is something many families don't know is an option until they're already in the middle of arrangements.

If more than one person wants to keep a part of their loved one close, you don't have to choose who gets the urn. You can use one adult urn to hold the full set of remains, and add as many keepsake urns as there are family members who want one. Each keepsake holds a small portion.

It's a way of sharing the memory rather than dividing it.

Our keepsake urns are sized and designed specifically for this, small enough to sit quietly on a shelf or bedside table, meaningful enough to feel like a proper tribute.

If someone in the family wants to carry their person with them every day, cremation jewellery works the same way. Pendants, bracelets and rings that hold a small portion of ashes close.

Understanding the Different Urn Types

Adult urns hold a complete set of cremated remains. Standard capacity is 200 cubic inches, which is 3.3 litres. This is what most families need for a single adult. Browse our adult urns.

Keepsake urns hold a small portion, typically a few tablespoons. Designed for sharing among family members, or for keeping alongside a larger primary urn. Browse our keepsake urns.

Companion urns hold the remains of two people, typically a couple. Capacity is usually 400 cubic inches or more. If you're making arrangements for two people who wished to be together, this is worth considering.

Extra large urns are for taller or larger-framed individuals where a standard 200 cubic inch urn isn't sufficient.

If You're Choosing an Urn for a Pet

The same rule applies, roughly 2.2 cubic inches per kilogram of body weight.

Our pet urns are 14×9.5×9.5cm, which gives a capacity of approximately 1.26 litres or 77 cubic inches. This comfortably fits pets up to around 35kg. For larger breeds, get in touch and we'll help you find a suitable option.

If you're not sure of your pet's weight, your vet will have it on record. Browse our pet urns — each product listing includes the capacity so you can match directly.

Frequently Asked Questions

What is a standard adult urn size in New Zealand? The industry standard is 200 cubic inches, which equals approximately 3.3 litres. This fits the remains of most adults and includes space for the sealed bag the crematorium returns the ashes in. If you see a capacity listed in litres elsewhere, a 3.0 to 3.5 litre urn is equivalent.

How do I calculate the urn size I need using kilograms? Multiply the person's weight in kilograms by 2.2 to get the approximate cubic inches of remains. A 75kg person produces around 165 cubic inches. A standard 200 cubic inch urn fits this comfortably, including room for the sealed bag. If the person weighed over 90kg, consider a larger urn.

Why do the remains come in a bag? Crematoriums return ashes in a sealed plastic bag inside a temporary container, usually a simple plastic or cardboard box. When you place the remains in the urn, the bag goes in as well. The bag takes up more space than the ashes alone, which is why the real capacity you need is typically 10 to 15 percent more than the weight formula suggests.

What happens if the urn is too small? The lid won't close properly, and forcing it risks damaging the urn or spilling the remains. If this happens, the options are to move to a larger urn, split the remains between a primary urn and one or more keepsakes, or contact the crematorium for guidance. We can help you work through this. Just get in touch.

Can I split the ashes between more than one urn? Yes, and many families do. One adult urn holds the full remains, and keepsake urns allow individual family members to each have a portion. There's no rule that says the ashes must stay together. What matters is that the choice feels right for your family.

What if I already purchased an urn and it's too small? This is more common than you'd think, and it's solvable. Message us and we'll help you find a suitable option, whether that's a larger adult urn or a way to split the remains into keepsakes so the urn you already have can still be used.

Is it okay to leave ashes in the temporary container from the crematorium? Yes. There's no rush. The temporary container is sealed and secure. Take the time you need to choose an urn that feels right, rather than making a hurried decision.

If You're Making This Decision Right Now

This week is hard. You don't need to get everything right immediately.

The ashes are safe in the temporary container while you take your time. If you'd like to talk through sizing, or work out how many keepsakes make sense for your family, message us directly. We're here, and we'll help you get it right.

Dan and Tania forever-urns.co.nz

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