Percentage Martingale

[Kiwi06]

Sorry if this is very basic but I can't seem to get my head around it

I am trying to create a spread sheet that can show me a balance and when i lose a trade how much i need to risk to of my current balance to recover the loss plus my Profit target E.G

Balance 200
Profit Target 205
Loss 5
Current Balance 195
Difference 10

This is for a forex trading system so it's kind of like a Martingale style system except with percentages

Any help would be great

[Kiwi06]

This might be right could someone please check it

[madsci64]

Assuming you still trade, please know that any martingale system is guaranteed to go broke. Eventually it will have a losing streak long enough to kill your account.

Here is an article that briefly introduces proper position sizing better than I can:
http://tradermike.net/2005/07/position_sizing/

Briefly, for a given entry/exit method, you need to know the win percentage, how much you win or lose, and variance of wins and losses (if any). Then pick a position size that risks a set percentage of your bankroll with each trade, balancing profit with avoiding ruin (account wiped out). You trade this same percentage each time, so you risk MORE when the account is bigger, and LESS when the account goes down.