Rates used here: Royal Mail retail (Post Office counter) prices effective 7 April 2026 and Click & Drop online prices effective 1 July 2026; Evri pay-online prices for delivery to a home or work address, as published on evri.com; DPD 2026 counter drop-off rates via Post Office branches; Parcelforce online-price-and-drop-at-a-branch rates effective 7 April 2026.
Three things this deliberately doesn't model, because they'd make the answer look more precise than it is. Courier collection costs more than dropping off — Evri, for example, charges £4.30 to collect a 0–1kg standard parcel versus £3.29 if you drop it off, so add roughly 75p–£1 per parcel if a driver comes to you. Volume accounts beat published rates — Evri's Frequent Seller tier (40+ parcels a month) and Royal Mail business accounts both price below the figures here, and if you're sending 100+ a month you should be on one. Remote-area surcharges apply — Evri adds a £2.75 location charge for some postcodes, and most couriers surcharge the Highlands, islands and Northern Ireland.
Marketplace-integrated labels (eBay, Vinted, Depop, Etsy) are often cheaper again than any public rate card, because the platform buys at bulk. If you sell through one, check its label price before booking direct.
Postage is the quietest margin killer in reselling. A £12 item sold on Vinted or eBay looks fine on paper until you take off the platform fee and then hand £4.79 to a courier for a parcel that could have gone for £2.85 — and that's before the mailer, tape and label. This postage cost calculator compares what Royal Mail, Evri, DPD and Parcelforce each charge for the exact parcel you're holding, then adds your packaging cost on top so you can see the real cost per dispatch rather than the headline postage price.
The cheapest way to send a parcel in the UK depends far more on size than on weight. Royal Mail's large letter format — anything under 35.3cm × 25cm × 2.5cm and 1kg — is dramatically cheaper than a small parcel, which is why experienced sellers flatten and repack rather than reaching for a box. Go one millimetre over on thickness and the price roughly doubles. This tool classifies your dimensions against each courier's size rules first, then shows only the services your parcel genuinely qualifies for, so you're not comparing a price you can't actually book. It also handles VAT: Royal Mail retail postage is exempt, while Evri, DPD and Parcelforce include VAT that a registered business can reclaim, which can flip the ranking entirely.
Not always, and increasingly not for light items. Royal Mail's Tracked 48 large letter is cheaper than any Evri parcel rate for flat items under 1kg, and Tracked 48 small parcel is competitive up to 2kg. Evri pulls clearly ahead in the 2–10kg range, where Royal Mail's medium parcel rates climb steeply. If you're VAT-registered, Evri's effective cost drops by a sixth because its prices include reclaimable VAT — Royal Mail's don't.
On Evri, DPD and Parcelforce, yes — their prices include VAT at 20%, and a VAT-registered business can reclaim it as input tax, making the real cost the price divided by 1.2. Royal Mail's standard retail postage is VAT-exempt, so there's no VAT to reclaim and the price you pay is the price it costs you. This is why the cheapest sticker price isn't always the cheapest option once you're registered.
For Royal Mail, a large letter must fit within 35.3cm × 25cm × 2.5cm and weigh up to 750g at the counter, or 1kg on Tracked services bought online. Exceed any single one of those and it becomes a small parcel — up to 45cm × 35cm × 16cm and 2kg — at a noticeably higher price. Depth is what catches people out: a soft item that fits the length and width can still fail the 2.5cm thickness gauge unless it's properly compressed.