The dimensions of urns differ considerably, so we look at the urn's capacity. How much ashes is produced after cremation depends on the person's body weight. There is one cubic inch of ash for every pound of body weight. So for a 300-lb person, you will need at least 300 cubic inches, but we always recommend getting a slightly larger urn.
The cremains of your loved one will weigh approximately 3.5% of their original weight. However, when it comes to the cremains of women vs. men, men typically weigh more. For example, the ashes of a 300-lb man will weigh around 10.5 lbs. The total weight of an urn with ashes will depend on the material of the urn. For example, with brass vs. aluminum urns, brass is the heavier of the two, ranging from 4–7 pounds, and aluminum is only 2–5 lbs.