What are the Royal Mail medium parcel size dimensions in cm?

A Royal Mail Medium Parcel can measure up to 61 cm long, 46 cm wide, and 46 cm deep, with a 20 kg weight limit. For rolled posters or tubes, the maximum length is 90 cm and length plus twice the diameter (L + 2D) can't exceed 104 cm.

What is the difference between a Large Letter and a Small Parcel?

A Royal Mail Large Letter allows dimensions up to 35.3 × 25 × 2.5 cm and a maximum weight of 750 g, designed to slide through standard UK home letterbox slots (25 mm). A Small Parcel permits up to 45 × 35 × 16 cm and a maximum weight of 2 kg. Large Letter rates are significantly cheaper than Small Parcel, making packaging thickness under 25 mm a key target for e-commerce sellers.

How should I measure my parcel dimensions?

Measure the maximum outer length (longest dimension), width (second longest), and thickness or depth (shortest dimension) including all packaging, bubble wrap, tape, and bulging contents. UK postal sorting offices measure the three-dimensional outer bounding box, so any bulge exceeding a limit will cause the parcel to be reclassified.

What happens if my package is slightly over the size or weight limits?

Royal Mail and UK sorting hubs use physical measuring gauges (aperture templates) and automated 3D optical volumetric scanners. If an item exceeds a slot by even 1–2 mm or exceeds the weight band, it is flagged as underpaid. The recipient will receive a grey fee-to-pay notification card with a surcharge (the postage difference plus an administrative handling fee), or the item will be returned to the sender.

Does this checker show live Royal Mail postage prices?

No. This tool is a size and weight band classification helper, not a live postage pricing calculator. Postal tariffs change periodically across services (1st Class, 2nd Class, Tracked 24, Tracked 48, and Special Delivery Guaranteed). Once you know your parcel band, check Royal Mail's website or your parcel shipping platform (such as Click & Drop) for current rates.

What is the difference between UK parcel size bands and dimensional (volumetric) weight?

Royal Mail consumer domestic services classify mail into fixed physical size bands with fixed maximum dimensions and weight caps. In contrast, international couriers (such as FedEx, DHL, and UPS) and air freight calculate dimensional weight (Length × Width × Height / divisor) and charge based on whichever is greater between physical scale weight and volumetric weight.

Can I send tubes or rolled posters as Small or Medium Parcels?

Yes. Royal Mail accepts roll and cylinder formats: for Small Parcel, the maximum length is 45 cm and the length plus twice the diameter (L + 2D) must not exceed 104 cm (max 2 kg). For Medium Parcel, the maximum tube length is 90 cm and length plus twice the diameter must not exceed 104 cm (max 20 kg).

UK parcel size checker

Classify your UK parcel dimensions and weight into official Royal Mail postal bands: Letter, Large Letter, Small Parcel, or Medium Parcel. Switch between centimeters, millimeters, grams, and kilograms to check size boundaries and avoid excess postage surcharges before posting. Runs client-side on your device with no data uploaded.

Client-side band helper · Royal Mail 2024–2026 limits · No live postage prices

Common items:

Length (cm)

Longest side

Width (cm)

Second dimension

Height / Depth (cm)

Thickness / depth

Weight (g)

Scale weight

UK Size ClassificationLarge Letter

Large Letter

Allowed up to 750 g for this format.

Sorted Dimensions

30 × 21 × 2 cm

Thickness (Depth)

2 cm

Parcel Weight

450 g

Band Weight Cap

750 g

Classification notes:

Fits within all Large Letter physical dimensions and weight limits.

UK Postal Bands Reference (Royal Mail)

Evaluated using cm & g

Band	Max Dimensions (L × W × H)	Max Weight	Typical Items	Fits Your Parcel
Letter	24 × 16.5 × 0.5 cm	100 g	Personal letters, Greeting cards, Invoices	Exceeds
Large LetterSelected	35.3 × 25 × 2.5 cm	750 g	A4 documents, Magazines, Slim books	Fits
Small Parcel	45 × 35 × 16 cm	2000 g	Shoes in box, Folded hoodies, Cosmetics hampers	Fits
Medium Parcel	61 × 46 × 46 cm	20000 g	Winter coats, Kitchen appliances, Bulky toys	Fits
Oversize / Courier	> 61 × 46 × 46 cm	> 20,000 g	Parcelforce, DPD, Evri Large, Pallets	N/A

Royal Mail 2024–2026 Consumer Format Specifications & Disclaimer

Size and weight limits are derived from published Royal Mail consumer format standards (royalmail.com/sending/uk/size-weight-limits).

This tool is a physical size and weight band helper, not live postage pricing. Royal Mail and courier postage prices vary by service (1st Class, 2nd Class, Tracked 24/48, Special Delivery) and change over time. Always verify parcel dimensions and check current rates with Royal Mail or your shipping platform before buying postage.

Related Shipping Calculators

Dimensional Weight Calculator Etsy Fee Calculator

UK parcel size checker example

A4 padded book mailer

A padded envelope measuring 30 × 21 × 2 cm weighing 450 g fits within the 35.3 × 25 × 2.5 cm and 750 g limits for Royal Mail Large Letter. If thickness expands to 2.8 cm, it steps up to Small Parcel.

UK parcel size checker how-to

Measure the packed item: longest side, middle side, and thickness, including tape and bulge.
Weigh it in grams or kilograms on a kitchen or parcel scale.
Enter the three dimensions and the weight. The page classifies Letter, Large Letter, Small Parcel, Medium Parcel, or oversize.
If you miss Large Letter by a few millimetres of thickness, flatten the pack before you buy postage.

Why UK parcel size checker matters

Royal Mail consumer services still sell on size bands, not dimensional weight. A 2.6 cm padded envelope that would have been a Large Letter is charged as a Small Parcel, which is a different product with a different price.

UK marketplace sellers (Etsy, Vinted, eBay) feel this on low-value items: postage can exceed the fee the platform takes. Checking the band before you list is cheaper than a surcharge card for the buyer.

This page does not quote live 1st Class or Tracked prices. Once you know the band, price it on Click & Drop or your carrier.

How the bands are applied

The checker sorts your three sides so length ≥ width ≥ height, converts mm/kg if needed, then tests published consumer maxima: Letter 24 × 16.5 × 0.5 cm / 100 g; Large Letter 35.3 × 25 × 2.5 cm / 750 g; Small Parcel 45 × 35 × 16 cm / 2 kg; Medium Parcel 61 × 46 × 46 cm / 20 kg. Tubes use length plus twice diameter. Anything larger is flagged oversize for a courier.

UK parcel size checker limitations

Consumer format guidelines, not a sorting-office gauge. Business, international, and tracked products can use different limits. Prices change; this tool does not store a tariff table.

Related guides

Royal Mail Large Letter vs Small Parcel
The thickness cap on Large Letter is 25 mm. Miss it and Royal Mail consumer postage steps up to Small Parcel.
How Etsy fees work for UK sellers
The 6.5% transaction fee applies to postage you charged the buyer, not just the item price.
Etsy vs Vinted fees for UK sellers
Same jumper, two fee models: seller commission versus buyer-side protection.
Dimensional weight divisors by carrier
The divisor, not the tape measure, decides whether a light box is billed as a heavy one.

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UK parcel size checker FAQ

What are the Royal Mail medium parcel size dimensions in cm?: A Royal Mail Medium Parcel can measure up to 61 cm long, 46 cm wide, and 46 cm deep, with a 20 kg weight limit. For rolled posters or tubes, the maximum length is 90 cm and length plus twice the diameter (L + 2D) can't exceed 104 cm.
What is the difference between a Large Letter and a Small Parcel?: A Royal Mail Large Letter allows dimensions up to 35.3 × 25 × 2.5 cm and a maximum weight of 750 g, designed to slide through standard UK home letterbox slots (25 mm). A Small Parcel permits up to 45 × 35 × 16 cm and a maximum weight of 2 kg. Large Letter rates are significantly cheaper than Small Parcel, making packaging thickness under 25 mm a key target for e-commerce sellers.
How should I measure my parcel dimensions?: Measure the maximum outer length (longest dimension), width (second longest), and thickness or depth (shortest dimension) including all packaging, bubble wrap, tape, and bulging contents. UK postal sorting offices measure the three-dimensional outer bounding box, so any bulge exceeding a limit will cause the parcel to be reclassified.
What happens if my package is slightly over the size or weight limits?: Royal Mail and UK sorting hubs use physical measuring gauges (aperture templates) and automated 3D optical volumetric scanners. If an item exceeds a slot by even 1–2 mm or exceeds the weight band, it is flagged as underpaid. The recipient will receive a grey fee-to-pay notification card with a surcharge (the postage difference plus an administrative handling fee), or the item will be returned to the sender.
Does this checker show live Royal Mail postage prices?: No. This tool is a size and weight band classification helper, not a live postage pricing calculator. Postal tariffs change periodically across services (1st Class, 2nd Class, Tracked 24, Tracked 48, and Special Delivery Guaranteed). Once you know your parcel band, check Royal Mail's website or your parcel shipping platform (such as Click & Drop) for current rates.
What is the difference between UK parcel size bands and dimensional (volumetric) weight?: Royal Mail consumer domestic services classify mail into fixed physical size bands with fixed maximum dimensions and weight caps. In contrast, international couriers (such as FedEx, DHL, and UPS) and air freight calculate dimensional weight (Length × Width × Height / divisor) and charge based on whichever is greater between physical scale weight and volumetric weight.
Can I send tubes or rolled posters as Small or Medium Parcels?: Yes. Royal Mail accepts roll and cylinder formats: for Small Parcel, the maximum length is 45 cm and the length plus twice the diameter (L + 2D) must not exceed 104 cm (max 2 kg). For Medium Parcel, the maximum tube length is 90 cm and length plus twice the diameter must not exceed 104 cm (max 20 kg).