Large Letter, Small Parcel and Medium Parcel limits, our checked online prices, how to measure, and the band mistakes that cost you money.
Updated 6 October 2026
Before you start
Large Letter, Small Parcel and Medium Parcel limits, our checked online prices, how to measure, and the band mistakes that cost you money.
Royal Mail prices a UK item by its format first and its weight second. Pick the wrong format and you either overpay or the buyer gets a surcharge card through the door.
Sizes below come from Royal Mail's size and weight guide. Prices are Royal Mail's online prices for labels you buy yourself, checked 6 October 2026, the day after the October price change. Counter prices at a Post Office are higher.
Kit for this
The products this guide uses, with typical UK prices.
500 g precision pocket scale
Card orders often sit within a few grams of a Royal Mail weight limit. A precise small scale tells you whether a mailer goes as a Large Letter or a parcel.
Typical price£8 to £14
See on Amazon
30 kg digital postal scale
Covers the parcels most home sellers ship, up to 30 kg. Choose it when the 40 kg scale is out of stock.
Typical price£12 to £20
See on AmazonKraft padded envelopes, D/1, 100 pack
Enough padding for a lipstick, a small figure or a sealed booster pack, with no box to fold.
Typical price£14 to £22
See on Amazon
Royal Mail Click & Drop
Imports orders from eBay, Etsy and other marketplaces, buys postage and prints to a thermal printer. Use it for the orders where you choose the courier; the platform labels its own.
Typical priceFree
Visit siteThe guide
Each step in the order you'll need it.
The four formats
Letter: up to 24 × 16.5 cm, 5 mm thick and 100 g. A thank-you card fits; most stock you sell will not.
Large Letter: up to 35.3 × 25 cm, 2.5 cm thick and 750 g. Small Parcel: up to 45 × 35 × 16 cm and 2 kg. Medium Parcel: up to 61 × 46 × 46 cm and 20 kg.
Large Letter prices
2nd Class Large Letter runs from £1.55 to £2.70 depending on weight, and 1st Class from £3.20 to £3.30 in our checked bands. Tracked 48 Large Letter costs £2.90 and takes up to 1 kg, more than the 750 g untracked limit.
A single trading card in a rigid mailer, a paperback, a silk scarf or a pair of earrings in a padded envelope sits here. Untracked Large Letters carry cover up to £20 and no tracking, so send anything pricier tracked.
Kit for this step
Small Parcel and Medium Parcel prices
Small Parcel: Tracked 48 costs £3.75 and 2nd Class £4.40 online. Tracked costs 65p less than untracked at this size.
Medium Parcel: Tracked 48 runs from £5.70 to £12.25 and 2nd Class from £7.00 to £13.70, stepping up with weight to 20 kg. Boxed trainers, a winter coat or a stack of hardbacks usually land here.
How to measure
Measure the packed item, with the mailer or box closed and taped. Length is the longest side, width the next, depth the thickest point, including any bulge from a zip or a buckle.
For Large Letters, use a slot gauge: cut a 25 mm slot in a piece of card and push the envelope through. If it sticks, Royal Mail's machines and counter staff will treat it as a parcel.
Weigh on a parcel scale with the label, tape and void fill on. Use a pocket scale that reads in single grams for Large Letters near a weight step.
Kit for this step
Band mistakes that cost you
A hoodie in a mailing bag that measures 3 cm thick at the hood is a Small Parcel, not a Large Letter. Fold it flatter, or pay the parcel price up front.
A box of 46 × 30 × 10 cm is 1 cm too long for a Small Parcel and jumps to Medium. Cut the box down or pick a 45 cm box. The same goes for 16 cm depth on a shoe box with a lid.
Underpaid items can reach the buyer with a fee to pay before collection. The buyer then complains, and you often end up refunding.
When another courier beats Royal Mail
For a buyer who will collect from a locker, InPost small at £1.99 beats any Royal Mail parcel for folded clothes. For flat items, use Royal Mail's Large Letter: the other couriers price a 2 cm envelope as a parcel.
Our postage price comparison covers the lockers and couriers in more depth.
Checklist
Run through it before each one goes out.
- 1Pack the item before you measure it
- 2Check thickness with a 25 mm slot
- 3Weigh with label and tape on
- 4Pick Tracked 48 over 2nd Class for Small Parcels
- 5Keep boxes under 45 × 35 × 16 cm for Small Parcel
- 6Buy labels online, not at the counter
Setups
Complete kits for one kind of seller, costed and laid out.
Questions
What is the maximum size for a Royal Mail Large Letter?
35.3 × 25 cm, up to 2.5 cm thick, and 750 g. Tracked 48 Large Letter takes up to 1 kg in the same size.
What size is a Royal Mail Small Parcel?
Up to 45 × 35 × 16 cm and 2 kg. Anything longer, wider, deeper or heavier goes as a Medium Parcel.
How much is a Small Parcel?
On Royal Mail's online prices checked 6 October 2026, Tracked 48 cost £3.75 and 2nd Class £4.40.
Do I measure the item or the parcel?
The parcel, packed and sealed. Royal Mail prices what arrives at the sorting office, bag, box and bulges included.
What happens if I underpay postage?
The buyer can be asked to pay a fee to collect the item. Check Royal Mail's help pages for the current charge.
Why are Post Office prices higher?
Royal Mail runs a separate, higher counter price list. Buy the label online or in Click & Drop and hand it over or drop it off.