Lot size will be defined by the amount on your account and your risk percentage.
You have 3% of risk planned and now I need the account balance.
Lot size is defined by the selected Volumen in the Metatrader 4 trading station.
If you want to trade EUR/USD trading pair and your account balance is in USD then 1 pip will be valued as:
Micro lot size = Volume = 0.01 gives 1 pip valued as $0.10.
Mini lot size = Volume = 0.10 gives 1 pip valued as $1.00
If you have $1000 on your account then 3% will be $30. To reach that you can open order with 30 pips stop loss with mini lot size.
If you have $1000 on your account then 3% will be $30. To reach that you can open order with 300 pips stop loss with micro lot size.
Account balance
Now define what is your account balance and use the desired lot size.
If $1000 is to much then use $100 where you will use micro lot size with 3% risk. That is $3 stop loss which gives you 30 pips area for the price fluctuation.
If you use less than $100 as a starting capital then just reduce the number of pips so you are inside 3% risk.
Hi thank you so much for this response that really helps
I wonder maybe could you help me with what leverage option to use with my broker? It says it ranges from 1:1 to 1:500. I need some help with understanding this and how it will effect my account etc.
The leverage defines how large lot size you will be able to open with available margin. That means the lot size will be limited to 0.01 or 0.1 or 1.0.
If you use large leverage broker will allow you to open higher lot size and the margin will be smaller. Meaning that if you have bad trade you could lose a lot before the margin call is activated.
Margin is the amount set aside which will remain after your trade is open.
When the trade is the closed that amount is returned to you.
To use the best leverage it depends on your account balance. If you have small balance like $100 then you should use small leverage.
1:20 is enough for you for using micro lot size which is 0.01.
If you want to learn more about the leverage please check here on this link where you can find examples how the leverage is calculated: