Position Sizing
Position sizing is deciding how many shares, contracts or coins to trade so that, if your stop is hit, you lose only an amount you chose in advance.
Most beginners ask “what should I buy?”. Experienced traders also ask “how much?” — and often treat it as the more important question. Two traders can take the same trade with the same entry and stop, and one survives a losing streak while the other does not, purely because of position size. This entry shows the formula, the reasoning behind it, and the numbers that make it matter.
- Category
- Risk Management
- Reading time
- 8 min
- Also called
- Position size, Trade size, Sizing
- Updated
Position sizing in plain words
Decide first how much money you are prepared to lose if the trade goes wrong — say $100. Then look at your stop loss: if each share would lose $2 before the stop is hit, you can buy 50 shares. If each share would lose $5, you can buy only 20.
The size of the position adjusts to the trade, so the money at risk stays the same. A wide stop means a small position; a tight stop allows a bigger one. Either way, a losing trade costs you the same planned amount.
How to size a position, step by step
This is fixed-fractional sizing — risking a fixed share of the account on each trade — the method most trading education starts with.
Place your stop where the trade is proven wrong
The stop should sit at a logical level on the chart, not at a random distance chosen to fit your money.1
Measure the risk per unit
Risk per share = entry price − stop price (for a long). For futures, it is the number of ticks to the stop multiplied by the value of one tick.
Divide and round down
Position size = money at risk ÷ risk per unit. Always round down, so rounding never increases the risk.
Check the position against your account
Make sure the position value makes sense for the account. If the stop is so close that the position becomes huge, the setup — not the formula — is the problem; if the stop has to be wide, buy fewer shares rather than risking more.2
Account for what can make the loss larger
Gaps, slippage and fees can push the real loss above the planned one, and positions in assets that move together add up to one larger bet.
Worked examples
Example 1 — Shares
SizingYour account is $25,000 and you risk 1% per trade. You want to buy at $40 with a stop at $37.50.
| Money at risk (1% of $25,000) | $250.00 |
| Risk per share ($40.00 − $37.50) | $2.50 |
| Position size ($250 ÷ $2.50) | 100 shares |
| Position value (100 × $40) | $4,000.00 |
| Loss if stopped at $37.50 | −$250.00 |
The position uses 16% of the account, but it risks only 1%. Position size and risk are different numbers — the stop links them.
Example 2 — Futures
SizingA $50,000 account risks 2% per trade, or $1,000. Each tick on the contract is worth $10.
| Stop 20 ticks away: 20 × $10 | $200 per contract |
| Contracts allowed ($1,000 ÷ $200) | 5 contracts |
| Stop 50 ticks away: 50 × $10 | $500 per contract |
| Contracts allowed ($1,000 ÷ $500) | 2 contracts |
The same logic as with shares: a wider stop means fewer contracts for the same dollar risk.3
Example 3 — Why the percentage matters: ten losses in a row
StreakLosing streaks happen to every strategy. Here is what ten consecutive losses do to a $10,000 account at different risk levels, each loss a fixed share of the current balance.
| 1% per trade | $9,044 (−9.6%) |
| 2% per trade | $8,171 (−18.3%) |
| 5% per trade | $5,987 (−40.1%) |
| 10% per trade | $3,487 (−65.1%) |
| Gain needed to recover from −65.1% | +187% |
At 1% a bad streak is an inconvenience; at 10% it is close to the end of the account. Recovering from a large drawdown takes a much larger gain than the loss itself.
Same risk, different stops, different sizes
Try it: position size calculator
Enter your account size, risk percentage, entry and stop. For a short position, put the stop above the entry. The calculation runs in your browser.
| Money you accept losing (1% of the account) | $100.00 |
| Risk per share (distance from entry to stop) | $3.00 |
| Position size | 33 shares (long) |
| Position value | $1,650.00 |
| Loss if the stop fills exactly at your price | −$99.00 |
The position uses 17% of your account. Remember: a gap can fill the stop at a worse price, so the real loss can exceed the planned amount.
Common ways to size positions
| Aspect | How it works | Strength | Weakness |
|---|---|---|---|
| Fixed dollar amount | Spend the same amount on every trade | Simple | Risk varies wildly with the stop distance |
| Fixed fractional (risk-based) | Risk the same % of the account to the stop | Constant risk per trade; shrinks after losses | Needs a defined stop for every trade |
| Volatility-based | Size from a measure such as ATR | Adapts to how much the asset moves | More calculation; still needs a risk budget |
| Maximum position cap | Limit any position to a % of the portfolio | Guards against concentration | Says nothing about risk to the stop |
Why position sizing matters
It keeps every loss survivable
With a fixed small risk, no single trade can do serious damage, however wrong it turns out to be.
It makes trades comparable
When each trade risks the same amount, results can be measured in R-multiples and strategies can be judged fairly. See R-Multiple.
It shrinks risk after losses automatically
Risking a percentage of the current balance means positions get smaller as the account falls, slowing a drawdown.
It removes a major emotional decision
Fear and greed most often show up as positions that are too small or too large. A formula takes that choice away.
Advantages and disadvantages
Advantages
- Keeps the loss per trade to a planned amount in normal markets.
- Works for any market: shares, futures, forex and crypto.
- Protects the account during losing streaks.
- Makes performance measurable in consistent units.
Disadvantages
- Depends on a stop: if gaps or slippage blow through it, the real loss is larger.
- Correlated positions can add up to far more risk than any single trade suggests.
- Small accounts may not allow fine enough sizes for some instruments.
- A low risk percentage feels slow, which tempts traders to abandon it.
Going deeper
Read as far as you need. Each level builds on the one before it.
Risk is not the same as position size
Beginner
A $5,000 position with a stop 2% away risks $100. A $1,000 position with no stop can lose $1,000. Always ask how much you lose if you are wrong, not how much you are buying.
Volatility, correlation and total exposure
Intermediate
Volatile assets need wider stops, so they get smaller positions; quiet assets can take larger ones for the same risk. Using a multiple of the Average True Range for the stop builds this in automatically.
Five positions in assets that tend to move together — five bank stocks, or five crypto coins — behave like one large position. Many traders cap total open risk, for example at 5% of the account across all trades, and limit how much of the portfolio any one position may use.
Leverage, gaps and the limits of the formula
Advanced
With leverage, the formula still tells you how much you can lose at the stop, but a liquidation price closer than the stop overrides it. Check that any margin or liquidation level sits well beyond the stop.
Gaps can fill a stop far from its price, so positions held through earnings, weekends or news should be smaller than the formula alone suggests. Some traders size those trades as if the stop were the likely gap level instead.
Common mistakes
Choosing the size first and the stop second
Buying a round number of shares and then squeezing the stop to fit puts the stop where the money says, not where the chart says. Choose the stop first.
Increasing size after a loss to “win it back”
Raising risk after losses is the fastest route from a drawdown to a disaster. See revenge trading.
Forgetting costs and slippage
Commissions, spreads and slippage add to every losing trade. Include them, especially in fast-moving or illiquid markets.
Ignoring correlation
Risking 1% on each of five closely related trades can amount to risking 5% on one idea.
Check your understanding
Test yourself before moving on. Each answer comes with an explanation.
Key points to remember
- Position size = money at risk ÷ risk per unit (distance to the stop).
- Choose the stop from the chart first, then size the position — never the other way round.
- Risking a small, fixed share of the account per trade keeps losing streaks survivable.
- Gaps, slippage, fees and correlation can make real risk larger than planned.
Frequently asked questions
Is 1% per trade a rule?
Should I risk a percentage of my starting balance or my current balance?
How do I size a position without a stop loss?
Does position sizing work in crypto and forex?
Further learning
- Stop Loss
Every position size starts from a stop.
- Risk-to-Reward Ratio
Once the risk is fixed, compare it with the potential reward.
- Leverage
How sizing interacts with borrowed money and liquidation.
- Drawdown
What sizing protects you from.
Sources
This article is written in our own words. The sources below support the specific facts, rules and figures marked with a number in the text. Links open the original publisher’s page.
- CME Group. Proper Position Size (opens in a new tab) Checked .
- Fidelity. Managing Risk with the One Percent Rule: What Is It? (opens in a new tab) Checked .
- CME Group. The 2% Rule (opens in a new tab) Checked .
Read more elsewhere
- Trading Metrics (our sister site): Position Sizing (opens in a new tab)
- Investopedia: Position Sizing (opens in a new tab)
Educational content, not financial advice. Examples use hypothetical prices and simplified costs; actual fees, margin rules and regulations vary by broker, market and country. Trading Metrics is our sister site, under the same ownership; we are not affiliated with any other publisher linked above. Last reviewed . Report an error or request a source credit.