Letter
- Maximum outer dimensions
- 24 × 16.5 × 0.5 cm
- Maximum packed weight
- 100 g
For a suitably packed thin envelope or card.
Royal Mail resources
ROYAL MAIL · ROYALMAILPARCEL
Royal Mail UK size & weight guide
Check a rectangular packed item against Royal Mail 1st Class format limits, then confirm the chosen product.
Sources reviewed
Check a rectangular packed item
Royal Mail 1st Class reference formats
This check uses the maximum dimensions and weights published for UK 1st Class. It finds the smallest reference format that fits your measurements. It does not choose a service, calculate postage or establish that the contents are accepted.
Reference-format result
Enter all four measurements, then check the reference format.
This checks maximum dimensions and weight only. Confirm minimum postal dimensions, the actual product, booking channel, contents and posting route separately. The result is a reference comparison, not an acceptance decision.
Compare postal servicesMeasurements stay in this page’s memory. Checking does not submit measurements, save a quote or reserve postage.
Reference maximums
1st Class maximum limits · largest side × next side × thickness
Large Letter
- Maximum outer dimensions
- 35.3 × 25 × 2.5 cm
- Maximum packed weight
- 750 g
For a thicker flat item within the reference limits.
Small Parcel
- Maximum outer dimensions
- 45 × 35 × 16 cm
- Maximum packed weight
- 2000 g · 2 kg
For a small box or packed item within all four limits.
Medium Parcel
- Maximum outer dimensions
- 61 × 46 × 46 cm
- Maximum packed weight
- 20000 g · 20 kg
For a larger or heavier rectangular packed item.
Each dimension and the packed weight must be at or below its limit. The check compares the entered decimal values without rounding them down. If a measurement is uncertain, remeasure the actual packed item.
Measure the item you will actually post
Jeton operational recommendation
Pack and seal first
Use the final outer packaging, protection and label arrangement. Measuring the goods before they are packed can understate the parcel’s dimensions and weight.
Measure the maximum outer size
Measure the largest outer extent in each of the three directions, including protruding packaging. Do not force a bulging packet flat to obtain a smaller thickness.
Weigh the complete item
Royal Mail’s heavy-item guide says to weigh the box with the goods and packaging. Enter grams here: 1 kg is 1000 g. If you repack or add protection, check the finished weight again.
Recheck before booking and handover
For Guangzhou consolidation or Edinburgh fulfilment, record the final packed measurements for each parcel after any repacking. Confirm the assigned postal service and its conditions before printing labels or authorising dispatch.
The format depends on the product and booking channel
A flat 900 g item is a useful example
Within 35.3 × 25 × 2.5 cm, a 900 g item exceeds the 750 g Large Letter reference used by this checker, so its smallest matching 1st Class format is Small Parcel. Royal Mail’s Tracked 24 page currently lists Large Letter limits of 750 g for Post Office purchase and 1 kg for online purchase. Confirm the actual product and channel instead of applying this result to every service.
Business accounts have their own product limits
The Business Tracked 24 and 48 page publishes a parcel maximum of 30 kg within 61 × 46 × 46 cm. That account product is outside this 1st Class reference check. Check your enabled service, account terms and chosen delivery option rather than treating 20 kg as a universal Royal Mail limit.
UK format is only one part of a China–UK plan
This checker does not evaluate international post, aircraft cargo, customs acceptance or a consolidation batch. Review those stages separately with the shipping partner. For actual weight, volumetric weight and chargeable-weight planning, use the general shipment calculator and confirm the quoted divisor and assessment rules.