Forex Lot Size Calculator for MT4 and MT5
Put your balance in and it returns the fixed lot to trade. There are two rules, one for your own money and a more conservative one for a funded account, and both are shown below so you can check the arithmetic yourself.
Lot size calculator
Enter your account balance and we will tell you the Fix_lot value to type into the EA.
Set Lot_mode to Fixed and Fix_lot to the value above. There is no upper cap: the lot keeps stepping up as the balance grows.
How the sizing rule works
There are two rules because there are two very different kinds of risk. On your own account the worst case is a drawdown you can sit through. On a funded account the worst case is a breach, and a breach is final: the account closes and the fee is gone. So the same balance is traded more conservatively when the money is not yours.
Your own account
0.01 lots up to 2,999, then one more 0.01 for every additional 2,000.
| Balance | Fixed lot |
|---|---|
| 0 to 2,999 | 0.01 |
| 3,000 to 4,999 | 0.02 |
| 5,000 to 6,999 | 0.03 |
| 7,000 to 8,999 | 0.04 |
| 9,000 to 10,999 | 0.05 |
| every further 2,000 | +0.01 |
A funded prop firm account
0.01 lots for every 5,000 of balance.
| Balance | Fixed lot |
|---|---|
| 0 to 4,999 | 0.01 |
| 5,000 to 9,999 | 0.02 |
| 10,000 to 14,999 | 0.03 |
| 25,000 to 29,999 | 0.06 |
| 45,000 to 49,999 | 0.10 |
| every further 5,000 | +0.01 |
Currency does not matter. Enter the number and ignore whether the account is denominated in dollars, euros or pounds. The steps are based on the size of the balance, not on the unit.
Where the number goes in MetaTrader
When you drag the Expert Advisor onto a chart its settings window opens. On the Inputs tab, set Lot_mode to Fixed and put the calculated figure into Fix_lot. Press OK and the value is live from the next tick.
Changing it later means removing the EA from the chart and adding it again with the new value, or opening its properties with F7. Positions already open are not affected by the change; only new ones use the new size.
The software does not resize itself. A lot set when the balance was 5,000 is still the lot it trades at 50,000. Re-check the figure whenever the balance crosses a step, otherwise you are trading a tenth of the size you intended, or ten times it.
Why fixed rather than percentage sizing
Percentage sizing sounds safer and often is not, particularly for a grid strategy. When a percentage rule scales the lot up after a winning run, it does so exactly when the next sequence has the most positions open, so the drawdown compounds twice over. A fixed lot that you review deliberately is easier to reason about, and much easier to check against a prop firm's daily limit.
It also means you decide when to increase risk, rather than an equation deciding for you on a day you were not watching.
Check it against your own limit
This is a sizing guide, not advice, and it cannot see your account. Two traders with the same balance can carry very different risk at the same lot size because their broker's leverage, spread, swap and stop level differ, and because a grid strategy holds several positions at once rather than one.
Before you trade real money, work out what the full sequence would cost you at this lot size if it ran to its maximum, and check that number against the loss you are actually prepared to take. If the two do not agree, trust your own limit and not the table.