Getting the shipping cost right on a listing is a balancing act that trips up plenty of sellers. Price it too low and you quietly lose money on every order; too high and buyers bounce at checkout. The fix is to stop guessing and work out your true cost, item by item, so the number you list is one you can actually afford.
Start with the real postage cost
The foundation is knowing what it actually costs to send the item, and that means weighing and measuring the finished, packed parcel, not the bare product. Weigh it, measure the dimensions, and get a real quote from your carrier for that exact parcel. The packed weight is always higher than the product weight, and ignoring the packaging is how sellers systematically underprice postage.
Add the label and packing costs
Postage isn't the whole cost. Add the label itself, the box or mailer, the tape and any filler, because those are all part of what it costs to ship. A label costs pence, a box costs tens of pence, and over a hundred orders that's real money you need to be charging for, not absorbing silently. Our packaging checklist covers what you're actually consuming.
Factor in your time
Packing takes time, and if you don't account for it, you're paying yourself nothing to pack. Estimate how long an order takes to pick, pack and label, and decide what your time is worth per hour. For a one-person business this is the cost most often forgotten, and it's the difference between a business and a hobby.
Don't forget the platform fees
If you sell on a marketplace, the fees apply to the shipping charge as well as the item price on most platforms, so a £3 shipping charge isn't £3 in your pocket. Check whether your platform fees shipping, and if it does, build that percentage into the number you charge so you're not losing a slice of every postage payment.
Decide between flat, calculated and free
Once you know your true cost, choose how to present it. Flat shipping is simple but averages out winners and losers across orders. Calculated shipping is accurate but can look expensive on heavy items. Free shipping converts best but needs the cost baked into the item price. The right choice depends on your catalogue, and our free vs paid guide walks through the trade-off.
Build a small cost table
The practical tool is a simple table for your main product types: item, packed weight, postage cost, packing cost, total. Work it out once per product line and you'll know your numbers instead of recalculating every time. It takes an afternoon and it removes the guesswork from every future listing you create.
Recheck when things change
Shipping costs drift, carriers raise prices every year, packaging prices change, and your product line evolves. Revisit the numbers when you add a product or when a carrier announces a price change, and you'll catch the drift before it eats your margin. A stale cost table is only slightly better than no cost table at all.
The margin check that matters
At the end, the number that matters is what's left after item cost, postage, packing, fees and your time. If that number is negative or too thin, the fix is to raise the item price, raise the shipping charge or lower your costs, not to hope volume makes up for it. Knowing your true shipping cost is what makes that decision possible.
Frequently asked questions
How do I work out my shipping cost? Weigh and measure the packed parcel, get a real postage quote, then add the label, packing and your time. That total is your true cost.
Should I use flat or calculated shipping? Flat is simpler, calculated is more accurate. The right choice depends on whether your items vary a lot in weight and size.
Do marketplace fees apply to shipping? On many platforms, yes, fees apply to the shipping charge too, so build that into the number you charge.
Keep the label cost low
Labels are a small but real part of the shipping cost, and our 100 × 150mm direct thermal labels keep that line item down so your margin maths works.
Shop 4×6 Labels