Ashes cremation urns come in a variety of sizes. The size you choose will depend on the amount of ashes you have, as well as your budget and the space you have available. A small urn may be sufficient for a child or pet, while a larger urn may be needed for an adult. Because ashes are skeletal remains, the volume is determined by the height of the deceased more than the weight.
A rule of thumb is that 1kg of body weight will result in about 36mL of ashes. This equates to 1lb prodcuing 1 cu in of ashes.
You may also want to choose a size that is appropriate for the number of people who will be sharing the urn. If you are unsure what size to choose, you can always consult with a funeral director or cremation specialist. They will be able to help you select an urn that is both practical and aesthetically pleasing.
For most adults, an urn that is at least 3 litres or 183 cubic inches should be sufficient.
Otherwise, the table below is a guide: