The number on your shipping invoice isn’t one price — it’s a stack of them. Base rate, surcharges, dimensional rules, zone math, speed premiums. Carriers understand every layer intimately. Most merchants understand one or two. That gap is expensive.
Here’s the full dissection, layer by layer, plus where growing brands can actually claw margin back.
Layer 1: The Base Rate
Every carrier publishes base rates for each service tier (economy, standard, expedited), tiered by weight and destination zone, and adjusts them annually based on operating costs, capacity, and demand — the famous general rate increase (GRI). Here’s the part that matters: base rates are a starting point. Enterprise shippers negotiate discounts and even caps on annual increases. Small shippers typically funnel all their volume to one carrier hoping loyalty earns a discount. It rarely earns much.
Layer 2: Surcharges
Surcharges are how carriers protect margins from costs their base rates don’t cover — and they’ve become a profit center of their own. The main types you’ll meet on an invoice: fuel, peak season, residential delivery, delivery area (remote zips), additional handling, and various inflation- and logistics-driven fees. They change throughout the year, they stack, and large shippers can negotiate waivers on some of them. Everyone else pays the published rate — often without noticing, because surcharges hide in the line items nobody reads.
Layer 3: Dimensional Weight
Carriers charge for space as well as pounds. Dimensional (DIM) weight converts your package’s volume into a theoretical weight: multiply length × width × height, divide by the carrier’s DIM factor, and compare against actual weight — the higher number is what you’re billed on. Since each carrier sets its own DIM factor (and a higher factor means a lower charge), the same box can be priced very differently across carriers. If you ship anything light and bulky, DIM rules should drive your carrier choice.
Layer 4: Shipping Zones
Domestic US shipping is priced in zones 1 through 8, measured from the package’s origin zip to its destination — not in miles. The more zones crossed, the higher the price and the longer the transit. Two identical packages to the same customer can cost wildly different amounts depending on where they start. Zone strategy — where your packages enter the carrier network — is one of the least appreciated levers in parcel.
Layer 5: Speed
Faster costs more, but the curve isn’t linear. Overnight is dramatically more expensive than 2-day; 2-day is a manageable step above ground. For most brands, the sweet spot is a reliable 2-to-5-day promise with an expedited option customers can pay for themselves. And if your packages enter the network close to your customers, ground can quietly deliver in 1–2 days at ground prices.
Putting It Together
Every layer of the rate stack rewards scale: negotiated base discounts, surcharge waivers, better DIM treatment, smarter induction. That’s the club small and mid-size shippers have been locked out of — and it’s exactly what Trellis opens up. We’re powered by one of the top domestic shippers in the US, and we pass enterprise rates, terms, and network strategy to growing brands: a custom carrier mix behind one rate card, one consolidated invoice, automatic invoice auditing, and up to 46% shipping cost savings. No volume requirements, no fulfillment commitment.
Want to see your own rate stack dissected? Get a free savings analysis at shiptrellis.com.
Frequently Asked Questions
What factors determine my shipping rate?
Five layers: the carrier’s base rate for the service tier, surcharges (fuel, residential, peak, handling), billable weight (the greater of actual and dimensional weight), the number of zones crossed, and delivery speed.
What is a general rate increase (GRI)?
The annual across-the-board price increase carriers announce, typically effective each January. Published GRI averages also understate most shippers’ real increases, because surcharge changes land on top.
Can small businesses negotiate shipping rates?
Technically yes, practically not much — carrier concessions scale with volume. Trellis solves this by pooling your volume with one of the largest domestic shipping operations and passing the negotiated rates and terms through to you.
What is Trellis?
Trellis gives growing ecommerce brands enterprise shipping rates, a managed multi-carrier network, invoice auditing, and full shipment visibility — with no volume minimums and no fulfillment commitment. It plugs into tools you already use, like ShipStation, Shippo, and ShipHero.