Is cheaper to use US credit card in UK?

Is cheaper to use US credit card in UK or is better to apply for UK ones? I mean taking in consideration the interes and the exchange rates.

You will pay a conversion fee (varies with each card) on every transaction if you use a US card, so if you are going to use it often, I would get a UK one.

The fee isn't large, in my experience, so you can use it to get on your feet. But it is best to get a UK one when you can.

yes, i wouldn't rely on it to make large purchases. i had to buy a new tv on my US card and paid over $25 in fees for just that one charge! 

Ow. I must've made all small purchases, I guess.

It would make very little sense to use a US credit card in the UK if you had the option of getting a UK card.

I think it depends on your situation in the UK.  If you're getting paid in pounds, a UK card is clearly cheaper.  If you're only in the UK for a few weeks or months, you're probably not going to be able to get a credit card. If all of your funds are in dollars, it may or may not be cheaper to use a US card.  Most american credit cards charge 2 or 3% of the total of each transaction.  You can find cards that only charge 1%(some credit unions) or 0%(capital one).