Royal Mail small or medium parcel? UK size limits and boundary examples

For UK sending, Royal Mail’s small-parcel format allows a maximum packed weight of 2 kg and dimensions up to 45 × 35 × 16 cm. A parcel must meet every limit. Royal Mail’s Tracked 24 page lists medium parcels up to 20 kg and 61 × 46 × 46 cm; check the particular service before booking. Small-parcel limits and Tracked 24 format limits.

The table describes rectangular parcels, rather than tubes or rolls. It is not a price quotation or a statement that every service accepts every listed format. Use the selected service’s size and weight information alongside its contents rules.

These worked examples apply the published limits. They assume ordinary rectangular boxes, accurate outside measurements and a service offering the relevant format.

A smaller result on one side does not offset an oversized measurement on another. These examples test the dimensions and weight only; they do not establish that the contents are permitted or covered for compensation.

Royal Mail’s measuring guidance identifies length as the longest side and asks senders to use metric measurements. Its weighing guidance includes the box and additional packaging. Royal Mail’s measuring instructions.

Our recommendation is to measure after sealing, including any bulge, and keep the three figures with the order. If your box supplier lists internal dimensions, measure the finished outside dimensions yourself. Do not assume the catalogue description is the measurement to declare.

If your tape uses inches, the length converter changes each measurement into centimetres. For example, 18 inches is 45.72 cm, which exceeds the small-parcel length limit even though “18-inch box” may sound close. The conversion uses 1 inch = 2.54 cm, as listed in the OSHA metric reference. Enter positive measurements and retain the unrounded value when checking a boundary.

For a scale reading in grams, use the weight converter: 2,000 g equals 2 kg. Enter the weight of the finished parcel, including packaging. The tool changes units; it does not round a parcel into an eligible service band.

Once the measurements are settled, compare the service’s delivery aim, tracking, contents restrictions and compensation terms against the order. Check the live booking price for that exact format and weight. Changing the box can change the booking details, so reweigh and remeasure before purchasing a replacement label.

For packing technique, use our packing and measuring checklist. For seasonal dispatch planning, see Royal Mail’s Christmas 2026 dates. The Royal Mail hub brings related coverage together.

Sources checked on 8 November 2026. Independent Parcel Insider guide for UK senders. Illustrative archive photograph by Sebastiandoe5, via Wikimedia Commons, taken in Wymondham in April 2021. Photo and displayed crop licensed CC BY-SA 4.0. Resized and cropped for display.