Two traders take the same trade, at the same price, with the same stop. One loses $20, the other $400. The difference does not come from the analysis: it comes from the lot size. Picking the lot "by feel", or keeping the same lot whatever the stop, means letting chance decide what a loss costs.
The right method is simple and goes in this order: decide how much you accept to lose, place the stop where the analysis requires it, and the lot follows.
The formula
lot = amount at risk ÷ (stop distance × value of one point for 1 lot)- Amount at risk: what you lose if the stop is hit. Usually a fixed percentage of the balance, for example 1%.
- Stop distance: the gap between the entry price and the stop, in points.
- Value of one point for 1 lot: what a 1-lot position gains or loses when price moves by one point.
The stop is placed first, where your trade idea is invalidated. The lot never decides the stop distance: a tighter stop "to be able to trade bigger" is a stop in the wrong place.
Where to find the right values in MetaTrader 5
The value of a point depends on the symbol and sometimes on the broker. Do not guess it: read it.
- In the Market Watch window, right-click the symbol, then Specification.
- Note the contract size, the tick size and the tick value.
- The value of a price move of one tick size, for 1 lot, is the tick value. For any move:
price distance ÷ tick size × tick value.
Also note the minimum volume, the volume step and your account currency. If your account is not in dollars, MetaTrader converts the tick value into your currency.
Example 1: EURUSD
A $2,000 account, 1% risk: $20. Stop placed 25 pips below the entry (0.0025 in price).
On most standard accounts, the contract size is 100,000 and one pip (0.0001) is worth $10 for 1 lot.
- Loss for 1 lot if the stop is hit: 25 × $10 = $250.
- Lot: 20 ÷ 250 = 0.08.
With a stop twice as wide (50 pips), the lot is halved: 0.04. The risk stays at $20.
Example 2: gold (XAUUSD)
Same account, same $20 risk. Stop $4.00 away from the entry.
At many brokers, 1 lot of gold is 100 ounces: a $1.00 move is worth $100 for 1 lot. Check it in the specification, as some brokers use other contract sizes.
- Loss for 1 lot: 4.00 × $100 = $400.
- Lot: 20 ÷ 400 = 0.05.
Gold moves fast: a $4.00 stop on an M15 chart is nothing unusual. If you kept the lot from the EURUSD example (0.08), you would risk $32 instead of $20, without having decided to.
Example 3: a synthetic index
On synthetic indices, contract sizes and minimum volumes vary a lot from one index to another. That is where reading the specification is essential.
Suppose the specification shows a tick size of 0.01 and a tick value of $0.01: for 1 lot, a 1.00 price move is then worth $1. A $2,000 account, $20 risk, a stop 300.00 away in price:
- Loss for 1 lot: 300 × $1 = $300.
- Lot: 20 ÷ 300 = 0.0667, rounded down to the volume step. With a 0.001 step: 0.066.
These values are a calculation example: use those of your own specification before applying the method.
Rounding, and knowing when to pass
The calculated lot rarely falls on a round number. Three rules:
- Always round down, to the volume step. Rounding up increases the risk.
- If the calculated lot is below the minimum volume, the trade is too risky for your account with this stop. Do not take the minimum volume "anyway": skip the trade, or wait for an entry that allows a shorter stop that is still justified.
- Add the costs if your stop is short: spread and commission come on top of the real loss.
Why 1% and not 5%
The percentage risked per trade decides what a losing streak does to you. And losing streaks happen to every method, profitable ones included.
| Risk per trade | After 10 losses in a row | Gain needed to recover |
|---|---|---|
| 0.5% | −4.9% | +5.1% |
| 1% | −9.6% | +10.6% |
| 2% | −18.3% | +22.4% |
| 5% | −40.1% | +67.0% |
At 1%, ten losses in a row are unpleasant. At 5%, they force you to make two thirds of the remaining balance just to get back to where you started. The ideal percentage depends on your method and your tolerance, but it is decided once, calmly, and does not change from one trade to the next.
Leverage does not change the risk
Leverage decides the margin locked to open a position, not what you lose if the stop is hit. With 1:500 leverage, you can open a much bigger lot than with 1:50; but with the same lot and the same stop, the loss is exactly the same. The danger of high leverage is that it allows lots your capital should not carry. The formula in this article protects you from that temptation.
Mistakes that skew the calculation
- Mixing up pips and points. On a five-decimal symbol, 1 pip is 10 points. A 25-pip stop is 250 points.
- Forgetting the account currency. On a euro account, the tick value is converted into euros.
- Keeping the same lot on every symbol. 0.10 lot on EURUSD and 0.10 lot on gold do not carry the same risk at all.
- Moving the stop after entering to "let the trade breathe": the calculated risk is then worthless.
- Opening several correlated positions (EURUSD and GBPUSD in the same direction, for example) while counting 1% for each: the real risk is closer to their sum.
Doing the calculation without mistakes
The calculation takes a minute by hand, but it is done under pressure, at the moment of entering, and that is when mistakes happen. Two solutions:
- a prepared spreadsheet, with the tick value of your symbols already filled in;
- a tool that reads the specification for you and calculates the lot from the chosen percentage. That is what Trade Manager Pro does: you set the risk as a percentage and the stop, it calculates the lot and places the stop.
Whatever the solution, keep the logic: the stop first, then the risk, the lot last.
The takeaway
A correct position size does not make a method profitable. It does something more important: it guarantees that a loss costs what you decided, and that a losing streak does not knock your account out of the game. That is the condition for your method's statistics to have time to play out.