Nikhil Sharma Tools
Free tool · No signup

How much of your shipping bill is paying for air?

Enter your box and weight. Get the DIM weight, the billable weight, and exactly how much you would need to shrink the box to stop paying the penalty. I run FedEx operations for a US Shopify brand daily; this is the math I run before every packaging decision.

-DIM weight (lb)
-Billable weight (lb)
-You pay for air

Why the divisor matters

DIM weight = (L × W × H) ÷ divisor, rounded up. At divisor 139, a 14×10×6 box is 7 lb billable even if it weighs 3. Negotiated contracts can move the divisor to 166, 194, or higher, which directly cuts billable weight on every light package. If you ship volume and have never asked about your divisor, that is money on the table. I audit FedEx and UPS invoices for DTC brands; book a call if you want yours read.

Common questions

What is dimensional weight?
Carriers charge for the space a package takes, not just its scale weight. DIM weight = L × W × H (inches) ÷ divisor. You are billed on whichever is higher: actual or DIM.
What divisor should I use?
139 for standard FedEx and UPS rates, 166 for USPS. If you have a negotiated contract, check it: some contracts carry 166, 194, or 250, and that single number changes your bill on every light package.
How do I stop paying DIM penalties?
Shrink the box. It is pure geometry, so half an inch off each side compounds fast. The tool above tells you the exact size where DIM stops exceeding actual weight for your item.

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