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Weigh the finished, packed box, measure its outside dimensions, and get a quote for the exact service level you want before you pay. Weight, size, distance, and speed drive the price, and flat-rate boxes change the math for heavy items.
Four inputs drive almost every quote: the packed weight, the box's outside dimensions, the origin and destination postal codes, and the service level. Weigh the box after packing, taping, and labelling it in your head, because cushioning, gel packs, and tape add weight people forget. Measure the outside of the finished box at its largest bulge in each direction, and round up. A carrier that remeasures your parcel will use its own numbers, so an optimistic measurement is the classic cause of a surprise billing adjustment after delivery. Keep a card with the finished size and weight of items you ship often, and quoting becomes a two-minute job.
Carriers charge by the greater of actual weight and dimensional weight, a size-based figure computed from the box's dimensions. A light, bulky parcel, such as a pillow in a large carton, can cost far more than its scale weight suggests because it eats truck space. This is why shrinking the box is often the cheapest move available: trimming a few inches off each side can drop the billable weight a full step. Flat-rate boxes dodge this entirely, since their price is set by the box rather than by weight or size, within the service's weight limit. For dense items that fit a flat-rate box, compare the flat-rate price against the measured-parcel quote; for light, bulky items, a smaller box usually wins.
| Cost driver | How it pushes the price |
|---|---|
| Actual weight | Heavier parcels cost more at every service level |
| Box dimensions | Large boxes bill at dimensional weight, even when light |
| Distance and zone | Cross-country and remote routes cost more than local ones |
| Service speed | Express and priority services cost more than standard ground |
| Extras | Signature, insurance, and pickup add to the base price |
Distance is priced in zones: nearby destinations sit in a low zone and cross-country ones in a high zone, with remote and northern addresses often drawing an extra surcharge on top. Speed stacks on distance, so the same parcel can have several valid prices depending on the service you pick, from a slow standard service to a next-day express one. A quote for one service level says nothing about another, so compare like with like when two sellers quote different numbers for the same parcel. Holiday peaks also matter: carriers add seasonal surcharges in the busiest weeks, and a quote pulled in October may not match the price in December.
Extras are where estimates go wrong. A signature requirement, added insurance, a pickup booking instead of a drop-off, and a rural or remote surcharge each add to the base price, and they are easy to forget when comparing quotes. Cross-border parcels add customs, duties, and brokerage-style fees that the label price never includes, and the recipient may be asked to pay them on delivery. Oversize and overweight thresholds are another trap: a box just over a length limit or a parcel just over a weight step can jump a full price band. Check the carrier's surcharge list for the service you chose, and read the quote's line items instead of only its total, so you can see which extra caused a jump.
Use the carrier's own rate tool or the checkout flow of the label seller, with your real numbers, and treat any quote from a third-party estimator as a rough range until the carrier confirms it. Enter the destination postal code exactly, including rural route details, since a wrong code can quote a city price for a remote delivery. If you sell online, quote the buyer from the same service you will actually buy, or build a small buffer into your shipping charge to absorb remeasurement adjustments. With LetterAgent, the flow is a per-label quote that you approve before paying: describe the parcel to your AI assistant, approve the exact quoted price, pay once through Stripe, and receive the label as a PDF. LetterAgent labels are Canada-only Xpresspost, flat-rate, with a five-kilogram maximum, so parcels over that weight or bound outside Canada need a different service.
Ready to ship it? Get a shipping label with LetterAgent: describe it to your AI assistant, approve the exact quoted price, and get your label.
LetterAgent is a working name. Prices include print, postage, and our service fee. US prices in USD, Canadian prices in CAD (Canadian prices exclude applicable sales tax, added at checkout). Currently in private testing.
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