Hi,
If you have an iPhone, there is a postage calculator on the App Store (I don't know about android), this is very easy to use. However if you're happy using the online 'Price finder', so be it.
Are you sure you're weighing the parcels correctly? Are the sides of the parcels resting on your work surface? Are you weighing the item only and not the item + packaging?
The PO uses a very simple algorithm to working out prices, for example below 100g will be a fixed price, say £1.50, 100-250g will be say £1.80 , 250-499 will be say £2.30 and so on.
And don't forget, recorded/signed for delivery adds 80p I think.
Also it could be your scales, it might sound daft, but If they are not 100% flat, the weight will be incorrect. As you said they are kitchen scales, they are hardly the most trustworthy instrument - as they do not need to be made to be 100% accurate. Also temperature plays a big part, as when the room temperature gets warm, all will expand, and contract when cold.
If you wanted to be super-correct, close all doors around you to ensure no draft is coming past, as this can also adjust the weight.
And to be super-super accurate, whilst weighing, don't be stood over the scales, as your body temperature and even you breathing can alter the result.
Whilst you're at the PO, and weighing your parcels, take a look at the spirit level built in to the scales (it's at the bottom left) , and check this is showing level too - it won't make a dramatic difference, but if your parcels are hitting 101g, you'll be paying more than a parcel weighing 99g.
And an obvious thing to do, before you put your parcel on ANY scales, make sure the display shows zero.
But tbh, it's probably just your scales. - thought I'd share some knowledge in laymans terms.
Adam
