Is there a good calculator to see how much BTC will buy of an altcoin?

i.e. Binance has a withdrawal limit, and I want to transfer just about the right amount of BTC to Binance, to buy a whole number of NEO, that I can actually then withdrawal to a wallet.

or, I want to just keep track of the fluctuating conversion rate, so I will know when it is a good time to buy.

Thanks!