UK Postage Rates For Envelope Sizes

British postage rates are dependent on the size of the envelope being mailed, with smaller envelopes being charged less and larger envelopes and packages being charged more. See also American Envelope Sizes & Postage Rates. The following classes of postage are available:


The small letter size attracts the lowest rate of postage and is suitable for standard business correspondance in the DL envelope, postcards, birthday cards and other small greeting cards. The following table gives the maximum dimensions for a small letter in millimetres and inches.

Dimension Max Size (mm/g) Max Size (in/oz)
Height 165 mm 6.5 in
Width 240 mm 9.4 in
Thickness 5 mm 0.2 in
Weight 100 g 3.5 oz


Thus you can post envelopes of sizes DL, C5, C6/C5, C6, C7/C6, C7, C8, C9 and C10 under the standard letter rate as long as they aren't too thick or too heavy.

If you wanted to use US envelopes in the UK you could send Lady Grey (A2), Thompson's Standard (A6), Besselheim (A7), Carr's (A8), Diplomat (A9), 6¼, 6¾, 7, 7¾, 8 5/8, and 9 using the small letter rate.

Pricing for Royal Mail 1st and 2nd class letter sevices can be found here.

Large Letter

The large letter size covers A4 sheets, magazines, CDs and DVDs in cases and many of the larger greetings cards. Large letter pricing is dependent on the weight of the item, with up to 100g being covered by the cheapest rate.

Dimension Max Size (mm/g) Max Size (in/oz)
Height 250 mm 9.8 in
Width 353 mm 13.9 in
Thickness 25 mm 1.0 in
Weight 750 g 10.5 oz


Envelopes of C4 size can be posted under the large letter postage rate, however a C3 envelope would be too large.

US envelopes of the following sizes are covered by the UK's large letter postage rate Willow (A10), 10, 11, 12, 14 and 16.


The UK Royal Mail now has four parcel classes, Small Parcel (wide), Small Parcel (deep), Medium Parcel and Rolls or Cylinders. The size and weight limits for each are as follows:

Small Parcel (wide)

Dimension Max Size (mm/g) Max Size (in/oz)
Height 450 mm 17.7 in
Width 350 mm 13.8 in
Thickness 80 mm 3.1 in
Weight (Max) 2kg 4 lbs 6.5 oz

Small Parcel (deep)

Dimension Max Size (mm/g) Max Size (in/oz)
Height 350 mm 13.8 in
Width 250 mm 9.8 in
Thickness 160 mm 6.3 in
Weight (Max) 2kg 4 lbs 6.5 oz

Medium Parcel

Dimension Max Size (mm/g) Max Size (in/oz)
Height 460 mm 18.1 in
Width 610 mm 24.0 in
Thickness 460 mm 18.1 in
Weight (Max) 20kg 44 lbs 1.4 oz

Postal Tubes

The maximum dimensions for Rolls or Cylinders (postal tubes) are 900 mm (35.4 in or 2 ft 11.4 in) length and the length plus twice the diameter of the tube must be no more than 1040 mm (40.9 in or 3 ft 4.9 in). So for a 900 mm length tube the maximum diameter would be 70 mm (140 divided by 2) or for a 500 mm tube the maximum diameter would be 270 mm (540 divided by 2).

The latest pricing for parcels can be found on the Royal Mail's Website., with tips on how to get the best value here.

The Small Parcel rate applies for Rolls and Cylinders less than 450mm (17.7 in) length, 80mm (3.1 in) diameter and 2kg (4 lbs 6.5 oz) in weight.

The parcel rate would allow C3 envelopes to be sent, however the limits would not cover a C2 envelope.

All larger items are required to be sent by the Royal Mail's courier service Parcelforce Worldwide.