Bitcoin Forum

Hi, i have a question. what if i sent my coins to some exchanges like mercatox or yobit  do i need an ETH (to cover gas transaction) to sell it? or no need?

you need need the transaction fee/gas when you are sending an on chain transaction. but after your deposit was complete on the exchange, you are in their database. there is no transaction fee/gas anymore because you are no longer making on chain transactions.

so when you want to sell any coin on exchanges you only pay trading fee which is usually a percentage of your order size. for example if you sell 0.1BTC worth of an altcoin on Yobit you will pay 0.2% of it or 0.0002BTC

Yes, you need eth to transfer your tokens. About gas you can check here https://ethgasstation.info on how many gas to use.

if it is simple transaction, use standart gas options

Yes. you need some amount of ethereum as a transaction fee (gas). It will not be a much of amount. 

You don't need any eth to do things on an exchange and neither to withdraw,
unless it's a decentralized exchange.

No need for gas because that is a centralized exchange but they have fees when you sell or buy. Unlike Decentralized exchange like Etherdelta you need some gas for every transaction.

No Gas fees are required to be paid while selling Eth on exchanges. Though there is some trading fee which automatically gets deducted from your exchange's account and varies from exchanges to exchanges. You would also be required to pay a small transaction fee when you withdraw your coins from exchange to your wallet.