Charge                    Weight

    1d                       1 ounce (maximum charge for letters to any destination)

    ½d                       for the next 1 ounce (or part of)
    ½d                       for each succeeding 2 ounce (or part of) (upto a maximum of 12oz)
    1d                        for every 1 ounce (or part of) over the 12oz limit

Unpaid letters were charged double rates.