Depop has a flat rate of 10% for items bought. There is the PayPal Fee of 2.9% + £/€0.30. This is only for UK/EU, if you reside in the US the PayPal Fee is 3.49% +$0.49 (according to Depop).
For transactions between the UK and EU there may be an additional 1.29% fee (seller service fee).For example, imagine you are a seller in the US that sold an item to a buyer for a total (item price and shipping charge) of $100 then the Depop Fee is $10 and the Paypal Fee is $3.98.
If you are a seller in the UK and your buyer is in the EU then your fees would be a total of £/€ 13.20 (10+2.9+0.30).