How E-Commerce Shipping Works
Shipping is rates, dimensional weight, SLAs and who pays. Rate shopping and packaging decide landed cost more often than the carrier brand on the box.
E-commerce shipping is the process of turning a paid order into a scanned handoff, a transit event, and a delivery (or a failed attempt). The storefront “shipping method” is the commercial wrapper. The invoice from the carrier or 3PL is a different document: billable weight, zone, service, and surcharges.
If you treat shipping as a $5 line you guessed at launch, it will eat contribution margin. Estimate pieces with the shipping cost calculator and see whether the offer still breaks even with the break-even calculator.
The path of a parcel
- Promise on the PDP and checkout (zone, ETA, cost).
- Pick and pack (warehouse or kitchen table—the physics are the same).
- Rate and label (service level, insurance, signature).
- Handoff (pickup, drop, or 3PL dock).
- Transit and exceptions (customs, weather, “customer not in”).
- Delivery or return to origin.
COD adds collection at the door and a higher return-to-origin (RTO) rate in many markets. Prepaid failures are more often address and payment than cash refusal—see Payment Failures and Checkout Recovery for the checkout side.
Rate shopping
Rate shopping means requesting prices from more than one service (or carrier) for the same pack and destination, then choosing on a rule: cheapest that meets the SLA, or a default service you can operationally run.
It fails when:
- The dimensions in the request are not the box you use.
- You rate as 0.5 kg and ship a 30 cm cube (dimensional weight).
- Origin is a warehouse in another city than the one in the rate card.
- You shop rates at checkout then print a different service in the warehouse.
Checkout-time rating should use the same pack catalog as the pack bench. If you cannot, use conservative default dimensions and eat the error as a known cost.
Dimensional weight
Carriers bill the greater of deadweight (scale) and volumetric weight:
Dim weight = (L × W × H) / divisor
The divisor is in the carrier’s tariff (and can differ by service and region). A light cushion in a large box can cost more than a dense spare part of the same scale weight.
Practical responses:
- Right-size cartons and mailers; do not default to one “safe” box.
- For apparel, consider poly mailers vs boxes when the product allows it.
- Put packaging SKUs in the product master (pack weight and cube), not in a sticky note.
Customs and remote-area surcharges are separate lines. International is a different product: duties, IOSS/DDP vs DDU, and who is importer of record.
SLAs
A service-level agreement in this context is the promise you make and the one the carrier makes to you. They should not contradict.
| Promise | Who must keep it | If it breaks |
|---|---|---|
| Cut-off (“ships today”) | Warehouse | False urgency, support load |
| Transit time shown at checkout | Carrier + your buffer | Refunds, chargebacks |
| Tracking within X hours | You + integrator | “Where is my order” |
| Delivery attempt rules | Carrier + customer availability | Failed delivery fees, RTO |
Do not show “next day” if the carrier’s cutoff is already past in that zone. Buffers exist because exception rates are never zero.
Who bears the cost
Someone pays the freight.
- Customer pays listed rate. Conversion is sensitive to sticker shock. Honesty at cart beats a $2 checkout line and a $14 capture.
- You absorb (“free shipping”). That is a discount. Thresholds can raise AOV if they are close to current baskets.
- Hybrid. Free in-zone, paid remote; or free above a threshold.
There is no morally superior option. There is only contribution. If you sell on marketplaces, fulfillment fees replace or add to this stack—marketplace fees and Amazon listings.
3PLs and platforms
A 3PL sells pick-pack plus often their carrier contracts. You still own the customer promise. Measure their scan time and exception rate, not only the all-in cost per order.
Platforms (Shopify, WooCommerce plugins) connect rates to checkout. They do not pack the box. Misconfigured default weights are a classic silent margin leak.
Packaging as a SKU attribute
Store pack weight and cube on the product (or on a pack recipe for kits). Checkout rating and warehouse labels should read the same fields. When marketing adds a gift box for December, dim weight changes—update the recipe or you will rate as a mailer and ship as a cube.
Hazardous, lithium, and oversized SKUs need service restrictions at rating time, not at the dock. A checkout that offers “express” on a SKU the carrier will reject is a conversion lie.
International and landed cost for the shopper
DDU vs DDP changes who pays duties. If the customer sees a low product price and a surprise customs bill, that is a conversion and support problem. Either quote duties or say clearly that they may be due. Do not hide it in a policy nobody opens.
Returns from another country are a different product: labels, broker, and restock. Contribution on export SKUs should include an expected reverse-leg cost.
Insurance and signature on high-ticket parcels are a cost vs loss tradeoff, not a default on every SKU. Signature can also increase failed-delivery fees if the customer is not home—model it like an SLA, not like a checkbox in the theme.
The longer operational map is the e-commerce shipping guide. Shipping works when the rate you charged, the label you printed, and the box you used are the same conversation.
Key takeaways
- The customer-facing rate is a commercial decision. The carrier invoice is billable weight, zone, and surcharges—often dimensional, not scale weight.
- Rate shopping across services only helps if packaging and origin postcode are honest in the rating request.
- SLAs (cut-off, transit promise, delivery attempt rules) are part of the product. Missing them is a refund and support cost.
- Whoever ‘bears’ shipping still pays: you in margin, or the customer in conversion. Model both with contribution, not with a flat $5 hope.
Frequently asked questions
What is dimensional weight?+−
Carriers charge the greater of actual weight and a volume-based weight (length × width × height / a divisor). Light, bulky packs often pay as if they were heavier. Measure the box you actually ship, not the product photo.
Should I offer free shipping?+−
Only if contribution still works after you put freight in the cost stack—or if a threshold raises AOV enough to cover it. Free shipping is a discount. See profit margin and AOV articles.
Do I need my own carrier contract?+−
Not on day one. Platform and 3PL rates are a start. As volume grows, negotiated rates and a 3PL can beat retail labels—if your packaging and zones match the quote you were given.
Related tools
- Shipping Cost Calculator
Build a landed shipping cost from weight, rate, packaging and handling.
- Break-Even Calculator
Find how many units you need to sell to cover fixed costs at a given price and variable cost.
Related guides
- E-Commerce Shipping Guide
Design shipping that you can fulfill: zones, packaging, dimensional weight, rate cards, returns, COD logistics and the messages customers see before they pay.
Related articles
- COD vs Prepaid Orders
COD can lift conversion and raise RTO, rejection and cash-cycle cost. Prepaid is cleaner operations. When COD is rational depends on your market and SKUs.
- E-Commerce Profit Margin Explained
Gross, contribution and net margin answer different questions. Channel fees, shipping and returns sit between list price and cash. Worked numbers included.
- Payment Failures and Checkout Recovery
Declines, retries and method mix lose more revenue than most homepage tests. Recover checkouts without collecting extra PII or bypassing payment security.