Why Exact Shipping Can Be Tricky — and What to Do Instead

You looked up a shipping rate, charged your customer that amount, and then the label cost something different when you actually bought it. Nothing is broken and you didn’t do anything wrong. A shipping quote is a price at a moment in time, not a price lock — and that’s true on every platform. Here’s why, and the three ways to stop it eating your margin.

Why a quote isn’t a price lock

When you calculate a rate, the carrier is answering one specific question: what does this package, with the weight and dimensions you entered, going to that address, cost to ship today?

Buy the label a few days later and any part of that can have moved. Carrier pricing and surcharges aren’t guaranteed to hold indefinitely. Neither are the package details — you might pack it differently than you planned, or the buyer might update their address.

A quote is an answer to a question you asked at a particular moment. It isn’t a promise about next week.

Your three options

Option 1 — Keep charging exact, but close the gap

If exact shipping is right for your items, the fix is timing. If you calculate the rate, collect the shipping, and buy the label close together, then there’s very little room for the number to move. Same day is ideal.

In practice that means treating it as one sitting: rate the package, charge it, print the label, done — rather than rating on Monday and shipping on Thursday.

Option 2 — Switch to flat or tiered

This is what we’d point most sellers toward, and not because it’s the lazy choice. A flat rate built from your own label history is accurate enough on average, and it takes the per-order lookup off your plate entirely.

How to set one honestly:

1. Pull your last 20–30 labels

   Look at what you actually paid, not what you charged.

2. Average it, then look at the spread

   If most labels land close together, a flat rate works. If they’re all over the place, go tiered — a base price plus a bit more per additional item, usually with a cap.

3. Set it once and let it fill itself in

   In your Accept Payment settings, under Payment, Shipping & Checkout Options. From then on the charge appears on every order without you looking anything up. See how automatic shipping calculation works.

4. Revisit it every few months

   Or whenever what you sell changes.

The goal is right on average, on purpose — not exactly right on every single package.

Option 3 — Coming soon: your buyer buys the label

We’re building buyer-purchased shipping labels at checkout. You enter the package details, and your customer purchases shipping at the rate available when they check out.

That closes the gap almost completely, because collecting the shipping money and buying the label stop being two separate events at two different moments. It’s not live yet — this is what’s coming, not what’s available today.

So which should you use?

• If your packages are mostly similar — flat rate.
• If the cost mainly depends on how many items someone buys — tiered, with a cap.
• If your items are genuinely unpredictable — heavy, bulky, wildly varied sizes — exact, bought the same day you quote it.
• If you run auctions or open bags — flat or tiered, because days will pass before you ship.

Common questions