Oyster card to Gatwick

[joshleb]

Heading to Gatwick this evening, and Ican't work out how much it will cost via Oyster card to get there.

I have a Z1-4 travel card currently, so how much on top will the Gatwick leg take, travelling from Clap Junction?

Anyone know any websites that could work it out

Cheers

[joshleb]

But as I've got a 1-4 oyster card, would some of that fare not be reduced?