Paypal Final Fee to checkout order of 3.4%

[ivanovitchi]

Appoligies for this post but i am completely new to this with some basic coding practise

I have set up a site to sell products
shipping is £8 in UK pounds

how do i get the checkout to add paypals final fee to the total?
example

goods cost £50
shipping £8
No tax required
Paypal adds 3.4% to final fee

total should read £50 + £8 + 3.4%

adding 0.034 will add 3.4% to the product itself and not the total cost of the product and shipping

So when the customer pays he pays 3.4% on the product and not the shipping fee which leaves me out of pocket???

any simple advise i would appreciate it