Check the likely Royal Mail format and calculate postage, packaging, collection fees and discounts.
This format check uses common Royal Mail maximum dimensions and weights. The final service, price and acceptance decision remain with the postal provider.
How to use the Postage Calculator UK
Weigh and measure the fully packed item. Enter the current price for the delivery service you want, then add the quantity and any packaging or collection cost. The calculator checks the likely item format and gives a transparent order total.
UK letter and parcel size guide
Royal Mail prices depend on format, weight, service and where postage is purchased. Measure the outside of the finished package because a padded envelope or box can move an item into a more expensive category.
| Format | Maximum dimensions | Maximum weight |
|---|---|---|
| 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 |
How postage cost is calculated
Postage subtotal equals the price per item multiplied by quantity. Any discount is deducted from postage only. Packaging is multiplied by quantity, while the collection or handling fee is added once. This makes it easy to separate the carrier charge from business fulfilment costs.
Use the current postage price
Postal prices can change, and online prices may differ from branch prices. Select the required delivery speed, tracking and compensation before entering the price. Check the official Royal Mail current postage prices for the latest available services and charges.
Plan related delivery and business costs
For local passenger transport, try the Taxi Fare Calculator UK. Vehicle contract costs can be checked with the Car Lease Cost Calculator UK. Online sellers can plan development expenses using the Website Cost Calculator UK. More tools are available on the United Kingdom Calculator homepage.
Frequently asked questions
Does the calculator choose a delivery service?
No. It checks the likely package format, while you enter the current price for the service you choose.
Should I measure the item before or after packing?
Measure and weigh the final sealed package, including the box, envelope and protective materials.
Are online and branch postage prices the same?
Not always. Check the purchase channel and enter the exact current price shown for it.
What happens if the package exceeds Medium Parcel limits?
The result flags it as outside the listed Royal Mail formats, so you can check another suitable carrier or service.
How is the discount applied?
The percentage discount applies to the postage subtotal only, before packaging and one-off fees are added.