Alexis Kestler
As a fellow trading geek, I‘m sure you‘ll agree that position sizing is one of the most important yet tricky aspects of trading. Determining the optimal trade size can have a huge impact on your risk management, profitability, and long-term success as a trader.
After testing dozens of position sizing techniques over my 10+ year trading career, I‘ve learned that the ideal way is to use a data-driven approach. In this comprehensive guide, I‘ll explain everything you need to know about position sizing, when to use different models, and how to leverage free calculators to size your trades like a pro.
Let‘s dive in!
What is Position Sizing and Why It Matters
Position sizing refers to the precise number of shares or contracts you buy or sell in a given trade. It decides the amount of capital you allocate to that trade.
The main goal of position sizing is to maximize potential profits while restricting the downside risk to an acceptable level in case the trade moves opposite your favor.
As a trader, you must walk a tightrope between opening either too large or too small positions:
- Over-sized positions can blow up your account due to excessive risk.
- Under-sized positions may limit profits and trading opportunities.
This is why position sizing is so crucial – it helps you balance risk versus reward intelligently and find the trade size "sweet spot".
The Perils of Improper Position Sizing
Let me share a real example to illustrate the dangers of poor position sizing.
When I first started day trading stocks, I used to buy 2000 shares of any stock I wanted to trade. Without any logical method, I assumed 2000 shares was the right amount simply because it "felt" correct.
One morning, I bought 2000 shares of a low float momentum stock at $10, with a stop loss at $9. I ended up hitting my max loss of $2000 when the stock swiftly dropped to $9.
At first, I thought losing $2000 wasn‘t a big deal as I still had $8000 left in my account. But over the next few weeks, I repeatedly lost $2000 per trade opening 2000 share positions. Within a month, my $10,000 account was completely wiped out!
This disaster taught me an unforgettable lesson – without a defined, data-driven position sizing rule, your account is as good as dead.
Since then, I‘ve religiously used position sizing calculations on every single trade. This has helped me maximize gains while minimizing losses, enabling consistent profits over many years.
Clearly, improper position sizing can doom your trading account due to:
- Overexposure to single trade risk
- Lack of trading longevity
- Failure to maximize winning trades
- Increased chances of hitting margin calls
- Highly inconsistent performance
In short, position sizing is the key to trading success. Mastering it helps gain an edge in the markets.
Different Position Sizing Models
Over the last several decades, traders have developed many position sizing models. Let‘s examine some of the most popular methods:
1. Fixed Percentage Risk Model
This simple approach entails risking a fixed percentage of your account on every trade.
For example, you may decide to risk only 1% or 2% of your total capital on each trade. If your account size is $10,000, you would risk $100 or $200 per trade.
The main benefit of this model is that losses are automatically limited due to the fixed risk percentage. This prevents account wipeouts.
However, some downsides are that profits may be limited on winning trades. Also, in periods of high volatility fixed percentage risk may become inadequate.
2. Fixed Dollar Risk Model
In this method, you risk a fixed dollar amount per trade such as $100 or $500. Your position size is based on how many shares or contracts you can trade to keep the risk at that fixed dollar level.
For a stock priced at $50 with a $49 stop loss, risking $100 would mean buying 200 shares ($1 risk x 200 shares = $200 risk).
Fixed dollar risk allows better control over the max loss per trade. But it also has limited profit potential per trade.
3. Kelly Criterion Model
This position sizing approach considers your proven edge in the market based on past win rate and risk/reward ratio.
It uses the Kelly percentage formula: Kelly % = Win Rate – (Loss Percentage / Gain Percentage)
You invest the Kelly percentage of capital on each trade. For example, if the Kelly % is 20%, you would risk 20% of capital on each trade.
The goal of Kelly sizing is to maximize long term capital growth. However, drawdowns can be higher.
4. Martingale Model
This is an aggressive compounding approach where you double your position size after losses, till you achieve a win.
If your first trade loses $100, you risk $200 on the next trade. After losing $200, you risk $400 and so on. When you finally win, it covers all losses and provides some profit.
Martingale is very high risk and can devastate accounts during losing streaks. But it has the potential for fast account growth with a high win rate strategy.
5. Fixed Fractional Position Sizing
This model determines position size based on your account, stop loss, and the upside profit target.
The formula is: Position Size = (Risk % x Account Size) / (Entry – Stop Loss)
The resulting position size gets a certain fraction of the account value based on the predefined risk % you want to take.
A benefit is limiting risk by capping it to a set percentage. A downside is that it may over-size positions for small stop losses.
6. Volatility Based Position Sizing
This approach dynamically calculates position size based on the market‘s volatility. Higher volatility means smaller position size.
One way is to divide your fixed risk amount by the Average True Range (ATR) of the security you are trading.
Volatility based sizing adapts your trade size to changing market conditions. But it requires continuously updating the ATR data.
As you can see, each model has pros and cons. No single method works perfectly in all market conditions for every trader. This brings us to the next important question – how to select the right position sizing technique?
How to Select the Best Position Sizing Method
The ideal position sizing model depends on your:
- Trading style (swing, day, scalp)
- Market volatility
- Account size
- Risk tolerance
- Profit objectives
- Win rate
Aggressive traders with a high win rate system can consider the Martingale or Kelly criterion models to maximize profits.
Conservative traders would be better off using fixed % risk or fixed fractional sizing to limit losses.
Day traders should use volatility adjusted position sizing that reduces size during volatile periods.
Swing traders can opt for fixed dollar risk since each trade is held for days or weeks.
Ultimately you have to test different position sizing models over hundreds of trades in your market and determine which one enhances your profitability while minimizing drawdowns.
For most traders (especially beginners), I recommend starting with the simple fixed percentage risk model of 1% or 2% of account per trade. This baseline method works reasonably well across different instruments and conditions.
Later once you gain experience, you can experiment with more advanced position sizing strategies. The key is to be flexible and evolve your method based on empirical data rather than blindly follow a rigid theory.
Now let‘s see how to actually calculate the proper trade size.
How to Calculate Position Size
While there are intricate mathematical formulas for position sizing models, the easiest way is to use free online calculators.
But it‘s still helpful to understand the key steps:
1. Determine Your Risk Amount
Decide how much you are willing to risk per trade based on your account size and risk tolerance. Common ranges are 1% to 5%. conservatively.
2. Identify Your Stop Loss
Determine where you will exit the trade if it moves against you. The stop loss exit point must be known before entering a trade.
3. Calculate Risk per Share/Contract
Subtract stop loss price from entry price to get the risk per unit.
For a stock bought at $50 with stop loss at $49, risk per share is $1.
4. Divide Risk Amount by Risk per Share/Contract
This gives the maximum shares or contracts that can be traded while staying within the preset risk limit.
If risk amount is $200 and risk per share is $1, then position size is 200 shares ($200 / $1).
5. Round the Position Size
Round the position size to the nearest feasible whole number considering account size, capital allocation limits per trade, and lot sizes.
Example Position Size Calculation
Let‘s do an example calculation using a fixed 2% risk model:
- Account Size: $10,000
- Maximum Risk: 2% of $10,000 = $200
- Stock price: $50
- Stop Loss Price: $49
- Risk per share: $50 – $49 = $1
- Position size = Risk Amount / Risk per share
= $200 / $1
= 200 shares
Therefore, we arrive at a position size of 200 shares to limit the total risk on this trade to $200 or 2% of our account value.
This example demonstrates how you can use a defined, mechanical process for determining trade size instead of blind guesswork.
10 Free Position Size Calculators for Easier Trading
While you can calculate position size manually, it‘s easier to use pre-built calculators that do the work for you.
Here are 10 of my favorite free online position sizing calculators for quickly determining your optimum trade size in different markets:
1. MyFXBook
MyFXBook offers a simple position size calculator tailored for forex traders.
Just plug in values for currency pair, account currency, account size, risk % of capital, stop loss price, and number of lots to trade.
MyFXBook will instantly calculate the ideal position size based on your inputs.
2. BabyPips
BabyPips also provides a handy currency position size calculator.
Enter your account size, currency pair, risk in percentage terms, and stop loss price.
Babypips will determine the optimal number of standard, mini and micro lots you should trade to limit risk.
3. ChartYourTrade
ChartYourTrade has a forex position size calculator with the added ability to set a trailing stop loss.
It lets you input currency pair, account size, risk amount, stop loss price (fixed or trailing), and leverage ratio.
This tool gives position size, risk per trade, total pips risked, and required margin.
4. InvestmentU
InvestmentU‘s calculator is designed for stock traders.
Just pick a stock symbol or index, enter entry price, stop loss price, account size and risk per trade % to get the number of shares to buy or short.
It also shows the total risk amount and risk per share.
5. EarnForex
EarnForex provides an advanced forex position size calculator for sophisticated traders.
Along with basic inputs, it allows entering trade details like fees, slippage, and partial closes. You can also customize the output fields displayed.
This gives you fine-grained control over position sizing calculations for complex strategies.
6. uFinz
uFinz hosts an in-depth stock position size calculator.
It accounts for slippage, fees, risk/reward ratio, and even shows full risk management statistics including sharpe ratio, probable ruin time, recovery factor, and more.
If you like analyzing the numbers, this is a great tool.
7. Rachana Ranade
Rachana Ranade is an educator who provides a simple position size calculator.
You enter capital amount, % stop loss tolerance, entry rate and target rate. It tells you the quantity to trade.
This tool is useful for basic position sizing in stocks and futures.
8. Intradayscreener
Intradayscreener caters to intraday stock traders.
It calculates shares quantity based on capital amount, daily risk %, total trades per day, and stop loss price.
Ideal for quickly finding your maximum trade size for executing multiple intraday stock trades within your risk limits.
9. Wealthy Retirement
Wealthy Retirement offers a clean stock position size calculator.
Handy for getting the number of shares to buy or short for your trade idea based on entry price, stop loss, account size and risk %. Also shows risk per share.
You can save and load previous position sizing calculations for quick reference too.
10. HFM
HFM provides a customizable forex position size calculator.
It calculates position size or margin required based on your inputs. You can modify parameters like pip size, currency, leverage ratio etc.
Great for configuring the calculator to your specific forex account parameters.
Using these free calculators makes finding the right trade size a breeze, saving you precious time and effort while trading.
Key Benefits of Position Sizing Calculators
Online position size calculators offer several advantages:
- Quick calculations – Get the ideal trade size in seconds instead of manual formulas.
- Ease of use – Simple inputs, user-friendly interface, minimal learning curve.
- Market adaptability – Find suitable calculators for stocks, forex, options, crypto.
- Risk control – Limit trade risk to a fixed % without errors.
- Strategy testing – Backtest different position sizing models easily.
- Account protection – Avoid account blowups from oversized trades.
- Consistency – Standard process for sizing any trades.
- Confidence – Trade right-sized positions without second guessing.
- Convenience – Access calculators anywhere on mobile or desktop.
Overall, position size calculators provide an efficient way to identify the optimum number of shares or contracts to trade based on your account, risk tolerance, and trading objectives.
Tips for Effective Position Sizing
Here are some tips to use position sizing effectively based on my trading experience:
- Start with fixed % risk model and low risk per trade like 1% or 2% of capital.
- Use stop losses on every trade before entering positions.
- Be flexible – adapt size for changing volatility and market conditions.
- Limit position size to only allocate a small % of capital to one trade.
- Reassess your model regularly and optimize based on backtest data.
- Make sure account has sufficient trading capital for right-sized trades.
- Adjust size dynamically based on current win/loss streaks.
- Don‘t fall prey to overtrading by taking excessively large trades.
- Use calculators to remove manual errors and emotional interference.
Following these tips will go a long way in boosting your trading performance through prudent position sizing and risk management.
The Bottom Line
Determining the right trade position size is a critical yet often overlooked factor among traders. In my experience, setting the trade size correctly:
- Transforms trading from gambling to a calculated business.
- Controls emotions and prevents impulsive trading.
- Removes greed & fear by following a defined risk rule.
- Maximizes profits while reducing account drawdowns.
- Enables consistency by enforcing risk parameters.
- Allows adjusting returns versus risks taken.
Mastering position sizing can mean the difference between achieving trading success and blowing up your capital. That‘s why every seasoned trader uses a logical method to identify the optimum number of shares or contracts to trade.
Online position size calculators eliminate the complexity of trade sizing calculations so you can focus on analyzing markets and profit opportunities. Use them judiciously to trade smarter, control risks, and grow your account.
Here‘s to profitable and stress-free trading! Let me know if you have any other tips for smart position sizing.
