Prior to 2013, Royal Mail guidelines classified parcels based on weight only. Since then, parcels are both measured and weighed before classification. Pricing was updated in March 2014, though the classification system itself remained the same.
All parcels are classified as either small, medium or large based on both their weight and dimensions, with postage costs calculated accordingly.
The following size and weight guide will help you calculate your postage and avoid unexpected costs.
Royal Mail Size & Weight Allowances – UK
Format | Max. Length | Max. Width | Max. Thickness | Max. Weight | Examples
Letter | 24cm | 16.5cm | 0.5cm | 100g | Standard letter, greeting card, postcard
Large Letter | 35.3cm | 25cm | 2.5cm | 750g | Small books, magazines, CDs & DVDs
Small Parcel | 45cm | 35cm | 16cm | 2kg | Books, clothing, toys, gifts
Medium Parcel | 61cm | 46cm | 46cm | 20kg | Clothing, footwear, household items
Note: Royal Mail now effectively treats “small parcel” as a single size format (your two-option version is outdated).
Large Parcels
Any parcel exceeding one or more of the medium parcel limits is classified as a large parcel and must be sent via a courier service (e.g. Parcelforce).
Exceptions
Rolled and cylindrical parcels:
Up to 45cm length and 8cm diameter (≤2kg) = small parcel
Larger items must not exceed length + 2 × diameter = 104cm, with no dimension over 90cm
Royal Mail Postage Costs (Updated April 2026)
1st Class
Weight | Small Parcel | Medium Parcel
Up to 1kg | £5.45 | £8.05
Up to 2kg | £5.45 | £8.05
Up to 5kg | - | £10.05
Up to 10kg | - | £10.05
Up to 20kg | - | £15.45
2nd Class
Weight | Small Parcel | Medium Parcel
Up to 1kg | £4.25 | £6.95
Up to 2kg | £4.25 | £6.95
Up to 5kg | - | £8.75
Up to 10kg | - | £8.75
Up to 20kg | - | £13.15
Key Notes (2026 updates)
Prices reflect Royal Mail changes effective 7 April 2026
Small parcel pricing is now flat up to 2kg (no price jump at 1kg)
Medium parcel pricing is tiered but flatter than older models
Compensation remains £20 included for standard services
Tracked services (Tracked 24 / 48) are now widely used alternatives
Large Parcels
Large parcels cannot be sent via standard Royal Mail services and require a courier (e.g. Parcelforce Worldwide). These services cost more but typically include tracking and delivery guarantees.
