How To Frank A Large Letter Or Parcel: 2026 UK Guide

Franking a standard letter is easy. You pick the service, pop it on the scale and feed it through. Large letters and parcels are where people trip up: wrong size band, the envelope's too thick for the machine, or the label goes on in the wrong place. Get it wrong and your mail could be delayed or charged extra.

Here's how to get it right every time.

Size and weight bands

Royal Mail prices by format first, then by weight. The format depends on the item's size and thickness, so measure before you weigh. These are Royal Mail's standard UK size limits (Royal Mail, checked October 2026):

Format	Max length	Max width	Max thickness	Max weight
Letter	24cm	16.5cm	5mm	100g
Large letter	35.3cm	25cm	2.5cm	750g
Small parcel	45cm	35cm	16cm	2kg
Medium parcel	61cm	46cm	46cm	20kg

A quick test: if an A4 sheet fits flat in the envelope without folding and it's no thicker than 2.5cm, you've got a large letter. Anything thicker, even a little, is a small parcel and costs a lot more.

Get yourself a cheap postal size template or a ruler with a 2.5cm slot. It pays for itself the first time it stops you underpaying.

Franked prices for large letters and parcels

These are Royal Mail's Mailmark franking prices from 7 April 2026 (Royal Mail Business Price Guide, checked October 2026):

Format	Weight up to	1st Class franked	2nd Class franked
Large letter	100g	£2.86	£1.52
Large letter	250g	£3.28	£1.81
Large letter	500g	£3.30	£2.30
Large letter	750g	£3.30	£2.50
Small parcel	2kg	£5.45	£4.25
Medium parcel	2kg	£8.05	£6.95
Medium parcel	10kg	£10.05	£8.75
Medium parcel	20kg	£15.45	£13.15

Royal Mail changed some parcel prices again on 5 October 2026, so double check your machine has the latest tariff downloaded before relying on the parcel figures above. Large letter prices weren't part of that change.

For the full picture, see our Royal Mail prices page.

Using labels

Most desktop franking machines can only feed envelopes up to a certain thickness, often somewhere between 5mm and 16mm depending on the model. Anything thicker needs a franking label.

Labels come in two types:

• Self adhesive rolls or sheets, which you peel and stick.
• Automatic label dispensers on bigger machines, which print and cut a label for you.

Where to put it: top right corner of the front of the item, the same place a stamp would go. Keep it flat, not wrapped around an edge, so the barcode can be scanned. Don't cover it with tape.

Our guide to franking labels covers label types in more detail.

Step by step: franking a large letter

1. Measure it. Check it's within large letter limits, especially the 2.5cm thickness.
2. Seal it properly. Loose flaps jam machines.
3. Select the format. On the machine, choose large letter, not letter. The machine needs to know the format to charge correctly.
4. Choose the class. 1st or 2nd, plus any extras like Signed For.
5. Weigh it. Place it on the scale and wait for the weight to settle.
6. Frank it. If it's thin enough, feed it through. If not, print a label.
7. Check the print. Make sure the impression and Mailmark barcode are clear.

Step by step: franking a parcel

1. Measure and weigh. Decide whether it's a small or medium parcel.
2. Check your scale limit. Small desktop machines may have a 2kg or 5kg scale. For heavier items, use an external weighing platform if your machine supports one.
3. Select parcel format and service.
4. Print a label. Parcels almost always need one.
5. Stick it on the largest flat face, top right, away from seams and tape.
6. Add the address clearly, with a return address on the back or top left.

Common mistakes

Calling a small parcel a large letter. This is the big one. If the item is thicker than 2.5cm, it's a parcel. Underpaid items can be surcharged or delayed.

Forgetting to switch format. The machine will happily frank a large letter at the letter rate if you don't change the setting.

Weighing on a wobbly desk. Unstable readings lead to wrong postage.

Squeezing thick envelopes through. It risks jams and messy prints. Use a label.

Using an out of date tariff. After a Royal Mail price change, machines need to download new rates. Most do it automatically, but check.

Labels on curved surfaces. Barcodes need to lie flat to scan.

A quick example

Say you're posting a hardback book in a padded envelope. It measures 30cm by 22cm, it's 3cm thick and weighs 600g. The length and width fit a large letter, but at 3cm it's over the 2.5cm thickness limit, so it's a small parcel. Franked 2nd Class at April 2026 prices, that's £4.25 rather than £2.50 as a large letter. If you can get the same book into slimmer packaging under 2.5cm, you'd save £1.75 on every one you send. For online sellers, that kind of packaging tweak is often worth more than the franking discount itself.

How to present your franked mail

Once it's franked, mail needs to be handed over correctly. Smaller volumes can usually go in a franked mail post box or be handed in at a Post Office, while larger volumes may need to be bundled and collected. Read our guide on how to present franked mail before your first big send.

Get into the habit of measuring first and weighing second, and most franking mistakes simply stop happening.

FAQs

Is franking a large letter cheaper than using a stamp?

Yes. A 1st Class large letter up to 100g costs £2.86 franked against £3.30 with a stamp, from April 2026 (Royal Mail, checked October 2026).

Can I frank a parcel with any franking machine?

Most current machines can, using a label. The limit is usually the scale. Heavier parcels need a bigger weighing platform.

What if my parcel is just over 2kg?

It moves up to the next band. Small parcels max out at 2kg, so anything heavier goes as a medium parcel.

Looking for a machine that handles parcels?

If you send lots of parcels, you'll want a bigger scale and an automatic label dispenser. Compare franking machine prices.