Lot Size for Scalping

Hi,
Im a newbie of course and have a couple of questions. I am creating a trading strategy using compounding and doubling my lot size when my account value has doubled in order to double the value of a pip which will double the amount of money i make(or lose) on a single trade. My question is what is the max lot size that one can trade before i start seeing issues with the order being filled? I got up to 800,000 units on my oanda demo account but i dont really trust it since it is a demo account.

Also whats the best site to read up on news that will affect the forex market?
and what is “Slippage”?

Thanks and love this site!!!
M. Blake

Some brokers “guarantee” certain volume on the execution of trades. If I remember correctly Dukscopy guarantee 100 standard lots before partial fills kick in. But as ever it comes down to market liquidity.

The demo account won’t have these problems with fills, as no one actually is buying what your selling or vice versa. Like Jezzode said, it’s a pretty high number before you start catching problems.

“Slippage” is where you place your order at one price, but it actually gets filled a few pips away. (Also when you’re selling). This can occur (frequently) in a big push up or a run down, as a bunch of people are trying to jump in. As you can imagine, it can really mess up your scalping.

Thanks for your responses!

I would like to answer my own question just in case someone else needs the info. Oanda trades up to 100 lots with no issues(from my research on the mt4 q and a section of the site) and myfxbook is a great site to read up on current events.