Dimensional Weight (DIM) or the Volumetric Weight is a parcel pricing technique used by shipping carriers. It uses the length, width, and height of a package to estimate a weight for it. The estimated weight is then used to calculate the shipping charges for the package.
The concept of dimensional weight is relatively a new one. It came into being after freight carriers realized that certain lightweight packages were occupying relatively higher volume compared to other products with similar weight. For instance, a stuffed toy when packed in a large box will occupy a large space, but the weight of the toy may not even touch a pound mark. So, from a freight carrier’s point of view, which calculates the shipping rates based on the weight, these low-density packages meant no profit. This resulted in dimensional weight being an industry-wide means of determining a reasonable charge for cubic space occupied by a package.
Calculation of Dimensional Weight (DIM)
Shipping carrier uses the formula (L*B*H)/DIM Divisor for the ‘Dimensional Weight’. This weight is then used to calculate the shipping charges for a package.
Let’s see the calculation of the dimensional weight of a box with an ‘actual weight’ of 1 pound.
- Start with taking a precise measure of the package. Since the dimensional weight is rounded off to the next whole number, precise measurements are going to be beneficial. For now, let’s take a commonly used ‘Large Flat Rate Box’ with outer dimensions i.e 12-1/4″ x 12-1/4″ x 6″. It costs you a flat $17.65 (commercial rate) so it will help us get an idea of USPS charges of a similar volume.
- Calculate the cubic volume of the package. In our example, it is going to be 900.375 cubic inches.
- Next, divide that volume with the DIM Divisor. The value of DIM Divisor is different for different carriers. It also differs for domestic and international deliveries. For instance, the DIM Divisor of USPS is 194 for domestic deliveries and 166 for international deliveries.
- On dividing the measured volume by the DIM Divisor i.e 900.375/194 we get 4.64 pounds, which is then rounded off to 5 pounds. So 5 pound is the dimensional weight of the package we are considering.
- Finally, compare this dimensional weight with the actual weight of the package. We have 5 pounds vs 1 pound situation. So the higher value, i.e 5 pounds will be taken as the billing weight for the package here. As we considered a box which has a flat fee of $17.65 so you can be sure that a box having a dimensional weight of 5 pounds is going to cost you more than $17.65.
The DIM Divisor is the frequency with which an additional pound is added to the dimensional weight of a package. Alternatively, you can say that it is the maximum volume a shipping carrier provides per pound weight of your parcel. For instance, the DIM Divider of 194 by USPS means that it will allow the maximum volume of 194 cubic inches for 1 pound of weight i.e one extra pound per 194 cubic inches increase in the volume of a parcel.
In terms of metric units, the equivalent of 194 cu in/lb is 7,000 cm3/kg. So as per USPS, a package taking 7001 cm3/kg will be equivalent to 2 kg in dimensional weight.
Shipping rates are based on weight and the weight used for calculating the shipping charge is called the ‘billable weight’. It is a function of the actual weight and the dimensional weight of the package. The larger of the two is taken as the billable weight. For instance, if the actual weight of a package is 7 lbs and the dimensional weight comes out to be 5 lbs, you’ll be charged for the higher one i.e. 7 lbs.
Points to Remember
- USPS applies DIM domestically to Priority Mail® parcels which are (a) larger than a cubic foot and (b) going to zones 5-9. So packages lesser than one cubic foot and going to zones 1-4 don’t go through dimensional weighing. One cubic foot = 12″ L x 12″ W x 12″ H = 1,728 cubic inches.
- In some cases ( Priority Mail® ) parcels within zones 1-4 only, and weighing less than 20 lbs, are charged with a USPS Balloon Rate pricing. So packages with girth “[Length (longest side)] + [(2xW)+(2xH)]” between 84″ and 108″, weight less than 20 lbs and being delivered to zone 1-4, will pay postage at the 20-pound rate rather than actual.
- Flat rate boxes are not a part of the dimensional weight.
- If the DIM weight exceeds 70 lbs, the shipping rates are calculated based on 70 lbs rate.
You can also find out dimensional weight with
DIM Divisor by Different Carriers
Here is a list if DIM divisors for domestic and international shipping by different carriers.
Measurements are in ‘cu in/lb‘.
Note: Australia post uses a formula [Height x length x width x 250 = cubic weight], where length are in ‘m’.
How to Reduce DIM costs?
Use Tamper Proof Plastic Courier Bags/Envelopes
Poly bags are strong and products of uneven sizes easily fit in them. These packing bags are not considered for dimensional weight. So you can eliminate dimensional weight in a lot of cases and send packages at regular weight-based pricing.
Choose Right Boxes
Let’s have an example for this. Consider three boxes with different dimensions.
- Box 1 has the dimensions 10″ x 8″ x 6″,
- Second box has dimensions of 8″ x 8″ x 8″, and
- The third box has the dimensions of 12″ x 8″ x 8″.
After calculating the dimensional weights for USPS international shipping of these boxes we get 3, 4 and 5 lbs. So you can calculate the dimensional weights of different boxes individually to find the one with the least DIM. You can also do this by using shipping plugins at ELEX, where different packing algorithms are designed to minimize the volume used to pack items in the order.
Best Packing Practices
You should keep the safety padding reasonable to reduce wastage of volume. Use standard materials so that you use less of them and still keep the products safe. Also, use multiple small boxes, with a volume less than 1 cubic foot, instead of a large box. Multiple small boxes will keep you away from the dimensional weight.
Use Multiple Carriers
USPS provides the cheapest domestic shipping rates corresponding to the dimensional weight of packages but FedEx and UPS are known to provide competitive international shipping rates. You can incorporate multiple shipping services by using two ELEX’s premium shipping plugins.
2015 was the year that marked the evolution of dimensional weight. From the illustration above you can easily find out why dimensional weight can mean business. Shipping carriers needed this concept to bring about the evenness in shipping charges and utilizing the trunk space for higher profits rather than incurring losses due to low-density packages. So when it comes to shipping, size matters.
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