Position sizing

What position sizing means

Position sizing is the process of deciding how large a trade should be. Rather than picking a lot size or share count by feel, you work backwards from the amount of money you are willing to lose if the trade fails and the distance between your entry and your stop-loss.

It is one of the few parts of trading that you can fully control. You cannot control whether a market goes your way, but you can decide how much of your capital is exposed to that outcome. For this reason many experienced traders and risk managers consider sizing more important to long-term survival than the choice of entry point.

Position sizing applies in every market: forex, CFDs, shares, ETFs, futures and options. The principle is the same, though the contract details differ, such as lot sizes, tick values, share prices or option multipliers.

How it works

The most common method is fixed fractional sizing, where you risk the same small percentage of your account on each trade. The steps are:

1. Choose a risk percentage per trade, for example 1 percent of account equity.
2. Convert it to money: risk amount = account equity × risk percentage.
3. Decide your stop-loss distance based on the chart or the instrument's volatility, not on how much you hope to make.
4. Calculate the money lost per unit if the stop is hit.
5. Position size = risk amount ÷ loss per unit at the stop.

Other approaches exist. Fixed-size trading uses the same number of units every time, which ignores differences in stop distance. Volatility-based sizing scales the position down when the instrument is moving more, often using an average true range measure. Some traders cap total exposure across correlated positions as well as each single trade.

Sizing must also respect margin. Even if the risk formula allows a large position, the margin required must fit comfortably within your free margin so a modest adverse move does not trigger a margin call.

A worked example

The numbers are illustrative only. A trader has an account of 10,000 euros and chooses to risk 1 percent per trade, which is 100 euros. They are trading EUR/USD and place a stop 40 pips from entry. For simplicity the account and pip value are treated in the same currency.

1. Risk amount = 10,000 × 0.01 = 100 euros.
2. Stop distance = 40 pips.
3. Pip value needed = 100 ÷ 40 = 2.50 euros per pip.
4. A micro lot of 1,000 units is worth roughly 0.10 per pip, so 2.50 per pip is about 25 micro lots, or 0.25 of a standard lot, which is 25,000 units.

If the stop were widened to 80 pips, the same 100 euros of risk would allow only half the size, about 12,500 units. The stop distance and the size move in opposite directions while the risk stays the same.

Why it matters

Sizing determines how survivable a losing streak is. Risking 1 percent per trade means ten consecutive losses reduce an account by roughly 10 percent. Risking 10 percent per trade means the same streak can wipe out most of it. Losing sequences are normal in any approach, so the size you use decides whether they are an inconvenience or a disaster.

Sizing also protects against the temptation to move stops. If the stop is placed where the idea is invalid, and size is adjusted to fit, you are not forced to widen the stop just to keep a large position alive.

Different account types shift the details. Leveraged CFD accounts allow large positions relative to deposit, which makes disciplined sizing even more important, while unleveraged share accounts limit exposure to the amount invested.

How to use it in practice

• Write down a maximum risk per trade and a maximum total open risk before you start trading.
• Place the stop at a level that makes sense for the market, then size the trade, not the reverse.
• Use your platform's position size calculator or a spreadsheet, and check the contract specification for pip, tick or point value.
• Account for spread, commission and likely slippage in the real cost of a stop being hit.
• Check margin required against free margin before sending the order.
• Reduce size when volatility rises or when several positions are driven by the same factor, such as a rising dollar.
• Record planned and actual risk for each trade to test whether you follow your rules.

Common mistakes and misconceptions

• Sizing by confidence. A feeling of certainty is not a measure of probability.
• Increasing size after losses to win it back, which compounds risk when you are least objective.
• Using the same lot size on every trade regardless of stop distance.
• Ignoring correlation, so three trades that look separate are really one large bet.
• Forgetting gaps and slippage, which can make a loss exceed the planned amount.
• Assuming a small risk percentage guarantees safety. It only reduces the damage of each loss.

Risks and limitations

Position sizing manages loss per trade but does not make a strategy profitable. Stops are not guaranteed in every product, and fast markets or overnight gaps can produce fills far from the stop, so actual loss can exceed the plan. Leveraged CFDs carry a high risk of rapid loss, and in some jurisdictions or account types losses can go beyond the deposit. Treat the formulas as a framework, not advice.

How Brokeli looks at it

Sizing depends on facts we check in broker research: contract sizes, minimum and maximum trade sizes, margin requirements, available stop types and whether negative balance protection applies. These details are recorded in the published research snapshot so you can compare them across brokers. We do not recommend any particular risk percentage; that choice depends on your own circumstances.