What size is a standard letter for royal mail

According to Royal Mail's guidelines, a standard letter is defined as a rectangular item with the following dimensions:

These dimensions apply to letters that are sent as "Large Letters" or "Large Parcels" in the UK. If your item exceeds these dimensions, it will be classified as a parcel and will require a parcel service.

It's worth noting that Royal Mail also has specific guidelines for the maximum weight of a standard letter, which is 100g (3.5 oz). If your letter weighs more than 100g, it will be classified as a parcel and will require a parcel service.

It's always a good idea to check the Royal Mail website or consult with a post office for the most up-to-date information on letter and parcel sizes and weights.