Shipping weight is more complex than placing a package on a scale. Carriers often use dimensional weight, a calculation based on the package's volume, to determine shipping costs. This means a theoretical weight calculated by multiplying the package's length, width, and height, then dividing by a standard divisor set by the carrier.
Understanding this concept is key to avoiding unexpected surcharges, improving your shipping strategy, and saving your business real money, something every smart business owner aims for.
Dimensional Weight Calculations by Carrier
Let’s break down how each carrier handles it:
1. UPS (United Parcel Service):
UPS calculates shipping costs based on either the actual weight or the dimensional weight of your package, whichever is greater. Dimensional weight is a way of accounting for the size of the package, not just how much it weighs. They use this formula (inches):
Dimensional Weight (lbs) = (Length × Width × Height)/166
This means that if your package is large but light, UPS might charge you as if it’s heavier because it takes up more space in their trucks. For international shipments, they use a different divisor, 139, but the concept is the same.
2. FedEx:
FedEx is on the same page as UPS with how they calculate shipping weight. They’ll charge you based on the higher of the actual weight or the dimensional weight. Their formula is slightly different:
Dimensional Weight (lbs) =(Length × Width × Height)/139
This formula applies to both domestic and international shipments. So, like UPS, FedEx makes sure that they’re fairly charging for the space your package takes up, even if it doesn’t weigh much.
3. USPS (United States Postal Service):
USPS has a slightly different approach, depending on the service you choose. For most packages sent with Priority Mail and Priority Mail Express, they use dimensional weight only if the package is over 1 cubic foot and being shipped to Zones 5-9. Here’s the formula:
Dimensional Weight (lbs) = (Length × Width × Height)/ 166
If your package is smaller than 1 cubic foot or you’re shipping to Zones 1-4, USPS will just consider the actual weight. This method is a bit simpler but still ensures that larger packages in higher zones are charged fairly.
Step by Step Guide on How Carriers Calculate Dimensional Weight
Let's take a closer look on how it's done:
Step 1: Measure the Package:
Measure the length, width, and height of the package in inches. Make sure to measure at the longest points, including any bulges or irregularities.
Step 2: Calculate the Cubic Size:
Multiply the length, width, and height of the package to get the cubic size in inches. For example, if a package measures 20 inches in length, 15 inches in width, and 10 inches in height, the cubic size is: 20×15×10=3,000 cubic inches
Step 3: Apply the Dimensional Weight Formula:
Each carrier uses a specific divisor to calculate dimensional weight from the cubic size:
UPS: Uses a divisor of 166 for domestic shipments and 139 for international shipments. FedEx: Uses a divisor of 139 for both domestic and international shipments. USPS: Uses a divisor of 166 for packages over 1 cubic foot shipped to certain zones.
Divide the cubic size by the carrier's divisor to get the dimensional weight.
Using the example above with UPS’s domestic divisor:
Dimensional Weight (lbs)= 3,000 cubic inches / 166 = 18.07 lbs Round up the result to the nearest whole number, so the dimensional weight would be 19 lbs
Step 4: Compare to Actual Weight:
Once you have the dimensional weight, compare it to the package’s actual weight. The carrier will charge based on whichever is greater.
Overview of Carrier Guidelines
Each primary carrier has its own set of guidelines for weight and dimensions. Understanding these can help you make informed decisions when selecting a carrier and managing your business's shipping rates, so we made this little quick aid to help you choose better:
USPS
| Type | Dimensions | Max Weight |
|---|---|---|
| Envelope | 12.5 x 9.5 | 70 lbs |
| Small Box | 8.69 x 5.44 x 1.75 | 70 lbs |
| Medium Box | 11.25 x 8.75 x 6 (top loading) | 70 lbs |
| 14 x 12 x 3.5 (side loading) | 70 lbs | |
| Large Box | 12.25 x 12.25 x 6 | 70 lbs |
UPS
| Type | Dimensions | Max Weight |
|---|---|---|
| Extra Small Box | 4 x 4 x 4 to 8 x 6 x 2 | 70 lbs |
| Small box | 6 x 6 x 6 to 12 x 9 x 2 | 70 lbs |
| Medium box | 8 x 8 x 8 to 13 x 11 x 2 | 70 lbs |
| Large box | 10 x 10 x 10 to 15 x 11 x 6 | 70 lbs |
FedEx
| Type | Dimensions | Max Weight |
|---|---|---|
| Small box | 9.5 x 12.5 | 9 kg (approx. 20 lbs) |
| Medium box | 11.5 x 2.375 x 13.25 | 9 kg (approx. 20 lbs) |
| Large box | 12.25 x 12.25 x 6 | 13 kg (approx. 28 lbs) |
Common Mistakes and How to Avoid Dimensional Weight Charges
-Ignoring Dimensional Weight: Always calculate actual and dimensional weights to determine which will result in the higher cost. This is vital when considering shipping charges by weight.
-Incorrect Box Size: Using a box that's too large can inflate the dimensional weight. Opt for carrier-provided packaging when possible. Checking the FedEx box size for shipping on their website can give you an idea of the standard box sizes available and help you avoid unnecessary costs. A little extra time searching for the perfect box will be required, but you’ll be glad you took that extra time. It is also a good idea to remember that you can use the carrier-provided package options and get the supplies from each carrier so they can avoid a future surcharge for dimensional weight.
-Not Including Packaging Weight: Ensure that the packaging is accounted for in the total weight. Forgetting this can lead to miscalculations when using a shipping weight calculator. Remember that boxes and cushioning add up to the total weight of the package.
-FedEx Shipping Charges: Dimensional weight is applied to all packages, with oversized items incurring additional fees. Understanding FedEx's pricing structure and how dimensional weight impacts your shipping cost by weight is critical.
-UPS Shipping Charges have similar rules to FedEx, with specific surcharges for oversized items. Understanding these charges can help you avoid unexpected fees.
-USPS Shipping Charges: Dimensional weight applies to larger packages; the postal service also has flat-rate options that can be more economical for heavy items. Knowing USPS shipping rates per pound and their impact on your business can be a game-changer.
Tips for Measuring a Package:
-Use a Tape Measure: Measure the length, width, and height of the package in inches. These measurements will directly influence the shipping charges.
-Round-Up: Carriers typically round dimensions to the nearest whole number, so it's better to round up your measurements. This ensures that your dimensional weight calculation is accurate.
-Consider Flat Rate Options: For heavy items, flat-rate shipping can be a cost-effective solution. USPS shipping rates for boxes often offer flat-rate options that can save you money.
Use AI to Choose the Right Box and Avoid Extra Fees
One of the most common mistakes we see in shipping is underestimating the cost of lightweight items, especially when they’re packed in oversized boxes. Even if your package feels light, if the box is large, you could end up paying based on dimensional weight, not actual weight.
Take the case of one of our long-time customers. She was shipping branded tote bags, super light, under two pounds, but packed them in large, flat boxes to avoid creasing. The result? Shipping costs were nearly double what she expected, because the carriers calculated the price based on size, not weight.
This is where our AI Shipping Assistant comes in. If you’re not sure how much your package weighs or how to choose the right box, just describe the item. Our tool will estimate the weight and recommend the best packaging to keep your costs low. It also shows you discounted rates from FedEx, UPS, and USPS so you can generate your shipping label directly from the tool, and make smart shipping choices on the spot.
Final Thoughts on Box Shipping Dimensions
Understanding shipping dimensions and weight is critical for efficient and cost-effective shipping. Following the guidelines and tips, you can avoid common pitfalls and optimize your shipping strategy.
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FAQs on Shipping Dimensions and Weight
How to calculate shipping weight?
To calculate shipping weight accurately, use a package weight scale and account for all packaging materials. This ensures that your shipping charges are based on accurate information.
Does shipping weight include the box?
Yes, always include the box's weight in your total shipping weight. This is essential for calculating accurate shipping charges by weight.
Does shipping go by weight or size?
Both. Carriers use either the actual or the dimensional weight, whichever is greater. To avoid overcharges, be sure to have an accurate scale when calculating shipping charges by weight.
What happens if shipping weight is wrong?
You may face surcharges, delays, or even package refusal. Shipping charges by weight aren't simple but require careful attention to detail.
What is dimensional weight?
Dimensional weight is a pricing technique used by carriers. It is calculated based on the size of the package rather than the actual weight. Calculating dimensional weight is crucial when shipping multiple packages that are the same size but not the same weight.
