Pack first
Measure after packaging, not before. Padding and boxes can change the size category.
Royal Mail and Evri guide
UK Parcel Size Checker
Use this UK parcel size checker and postage guide to compare packed parcel dimensions and parcel weight with small parcel, medium parcel, and courier limits.
Prices are estimates, not checkout quotes. Public Royal Mail and Evri prices were checked on 9 June 2026. Always confirm the final price and restrictions with the carrier before posting.
Check your packed parcel
Measure the item after adding its box, mailer, padding, tape, and label.
How it works
Dimensions are checked in size order
The tool sorts your three dimensions from largest to smallest before comparing them with Royal Mail's Letter, Large Letter, Small Parcel, and Medium Parcel limits.
Weight matters as well as size. A compact but heavy parcel may move into a different service or exceed a courier limit.
Royal Mail maximum formats
- Letter: 24 × 16.5 × 0.5cm, up to 100g
- Large Letter: 35.3 × 25 × 2.5cm, up to 750g, or 1kg with Tracked 24/48
- Small Parcel: 45 × 35 × 16cm, up to 2kg
- Medium Parcel: 61 × 46 × 46cm, up to 20kg
Evri is checked separately because it uses weight bands and a length-plus-girth rule.
Packing tips
Measure what you will actually send
Round up
Round dimensions and weight up rather than down when buying postage to allow for small measuring differences.
Check the courier
Confirm current maximum dimensions, weight, restricted items, compensation, and prices on the courier's own website.
Common mistakes
Avoid an unexpected postage adjustment
Measuring the item alone
Measure after packaging because the box, mailer, padding, tape, and label all count towards the final parcel dimensions.
Rounding down near a limit
A small difference can move a parcel into another band. Round uncertain measurements and parcel weight up before buying postage.
Assuming every courier agrees
Small parcel and medium parcel rules differ between carriers. Check the chosen courier's current rules before posting.
Common questions
UK parcel size FAQ
Should I measure my parcel before or after packaging?
Measure after packaging. Include the box or mailer, padding, tape, label, and any outer protection.
Does this tool show exact postage prices?
No. It shows dated public estimates. The final carrier quote can vary by service, destination, extras, collection method, and future price changes.
Why does parcel weight matter?
Couriers normally apply both size and weight limits. A parcel can fit the dimensions but still be too heavy for a particular category or service.
Which courier should I check before posting?
Check the carrier you intend to buy from. Compare its current price, parcel limits, delivery speed, drop-off options, tracking, compensation, and restricted-item rules.
Official sources: Royal Mail UK services and prices, Royal Mail 2026 price guides, Evri size and weight guide, and Evri prices.
Related seller tools
Estimate note: Size bands and postage prices are a dated guide. Buy postage using the carrier's final quote and current restrictions.