The purpose of dimensional weight pricing is to calculate FedEx, UPS, and USPS shipping costs factoring in the amount of space a parcel will take up and charge accordingly. The space each package occupies is at a premium, thanks to a growth in eCommerce shipping. Space has become a precious commodity.
Generally, if your package is heavy or small, you don’t need to worry about DIM prices. You’ll pay for carrier shipping based solely on the actual package weight. However, if you ship something relatively light in a large box, you may pay more than you usually expect due to DIM weight pricing.