When choosing a cremation urn, one of the most common questions people ask is, "How much ash fits in an urn?" Selecting the correct urn size is important because it ensures your loved one's ashes are stored safely and respectfully. Many people are surprised to learn that urn sizes are measured in cubic inches, not by height or width. In this guide, you'll learn how cremated remains are measured, how to calculate the right urn capacity, and which urn size is best for your needs.