Pricing in Proportion

what is it?
In 2006 the Royal Mail copied many other countries and changed the way mail is charged for by introducing Pricing in Proportion or PIP.

What is Pricing in Proportion? .
Without Pricing in Proportion it costs Royal Mail more to sort, handle and deliver larger envelopes and packages than they were currently charging customers to send. Large and irregular shaped packages take up more space in postbag’s and vans and cost more to handle. This mean t that most light but bulky items were priced below cost, whereas smaller, heavier items were generally overpriced. So the Royal Mail changed to Pricing in Proportion system to more accurately reflect their costs.
Before all post needed to be weighed to determine the postage rate, but with pricing in proportion not only the weight is required but also the size. This includes width, length and thickness.
Letters Size Guide

The Letter size for Pricing in Proportion the item needs to be less than 100-grams in weight no more than 5mm in thickness and no more than 240mm x 165mm. Just a bit bigger then a A5 or c5 envelope.
You can get 3 x A4 sheets folded 2 times for a DL envelope in this category or in a C5 envelope you can get 6 x A4 folded once.

The post that many people forget about pricing in Proportion is when something is put into the envelope like a badge or pen because this is enough to bring it up to the next level. People have had problems with celebration cards Birthday etc in the past because they forget to take the badge or something similar into consideration. When you buy a birthday or anniversary card look on the back and quite often you will see it tells you which postage you require.

This is the postage measurements

240mm x 165mm
(just over A5)
353mm x 250mm
(just over A4)

450mm x 350mm

610mm x 460mm

Here are some examples where it may get confusing which postage to use.
Let’s say you have to send a glasses case to someone because they forgot to take it with them home.
It weighs less than 100 grams but because it does not fit through either slot in pricing in proportion it has to be sent as a packet.

The postage therefore would be £2.70 1st class or £2.20  2nd class.
Another example is a CD. This would go as a Large letter again as it will not go through the small slot.
If you have a Letter Price size guide please remember that the letter or package
MUST FALL THROUGH THE SLOT FREELY . It will not be accepted by the Royal Mail if it “sticks “at all at that price point.
If you are unsure if it will be accepted at that price point, I would suggest you put the higher postage on.
If the Royal Mail declines your mail for being the wrong size at the price point you have used. They will charge the recipient £1.20 plus the difference of your postage value and the next postage value up at 2nd class.
So for an example let’s suppose you put on an envelope a 1st class stamp. When it is sorted and does not got through FREELY the slot for a letter size it is a Large Letter. The price of a Large letter is 90p 1st and 69p 2nd.
The Royal Mail will charge £1.20 plus the difference between the postage the envelope has on it and the next level at 2nd class.

Therefore the recipient of your letter will have to pay £1.29. i.e., 60p from 69p = 9p plus £1.20 =£1.29

Royal Mail Letter size guide