1st Lot from % of Balance
For a more "fair" (at any time of the test start) DD, I suggest calculating the 1st Lot as a % of the Balance
Look
Lot/1000 = 0.1
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Balance 1000
1.01 open 0.1
10.01 profit +900 Balance= 1900
15.01 open 0.1
20.01 DD 80% (-1520)
25.01 profit +200 Balance= 2100
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Balance 1000
15.01 open 0.1
20.01 DD (-1520) Stop Out
Here we do not see in the first test run that we "suffer a fiasco" at the start from 15/01
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And here we see...
Lot = 1%/Balance
--
Balance 1000
1.01 open 0.1
10.01 profit +900 Balance= 1900
15.01 open 0.19
20.01 DD (-1520*0.19/0.1=-2888) Stop Out
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Lot = 0.5%/Balance
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Balance 1000
1.01 open 0.05
10.01 profit +450 Balance= 1450
15.01 open 0.07
20.01 DD (-1520*0.07/0.1=-1064)
25.01 profit +140 Balance= 1590
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Balance 1000
15.01 open 0.05
20.01 DD (-1520*0.05/0.1=-760)
25.01 profit +100 Balance= 1100
Stop Out is not happening
% from balance is equal to 'lot per 1000'
The only difference is in change step. Lot per 1000 works bad for very small deposits. But it is not a problem for live trading, I guess.
And, finally, you can use "Margin percent use". It will work like % from balance for the first deal.