Calculating Position Size in Trading

Calculating Position Size in Trading


Proper risk management is crucial regardless of the size of your portfolio. Failure to make an appropriate strategy to handle risks can lead to significant losses and the complete depletion of your account, erasing weeks or even months of progress in a single trade mismanagement.

One of the fundamental goals of trading and investing is to avoid making emotional decisions. Given the involvement of financial risk, emotions play a substantial role that must be kept in check to prevent their interference with your trading and investment choices. Establishing rules to abide by during your trading and investment activities proves invaluable in this regard.

We shall refer to these rules as your trading system, serving the dual purpose of managing risk and eliminating unnecessary decision-making. With a well-defined trading system, impulsive and hasty decisions become a thing of the past.

When constructing these systems, several factors need consideration. What is your investment horizon? What is your risk tolerance? How much capital are you willing to put at stake? While numerous other factors exist, this article will concentrate on a specific aspect: determining the appropriate position size for individual trades. To achieve this, we must first ascertain the size of your trading account and the amount you are willing to risk on a single trade.

Optimizing Portfolio Allocation for Trading Strategies

Allocating your portfolio effectively among various strategies is crucial, even if it may appear simple or repetitive. Particularly for beginners, this approach aids in accurately monitoring progress and mitigating excessive risk exposure.

To illustrate, suppose you possess a long-term belief in the potential of Bitcoin and hold a position safely stored in a hardware wallet. It is advisable not to include this position when determining your trading capital.

Thus, determining the account size entails examining the accessible capital that can be assigned to a specific trading strategy. By doing so, you can methodically track the progress of each strategy while reducing the likelihood of excessive risk-taking.

Calculating Account Risk

The subsequent stage entails the calculation of account risk, encompassing the determination of the portion of your available capital you are willing to expose to risk in a single trade.

Adapting the 2% Rule for Crypto Trading

The 2% rule is a widely recognized investing strategy in traditional finance, emphasizing that traders should not risk more than 2% of their account on a single trade. While we will delve into its precise implications, let us first tailor it to suit the dynamic nature of cryptocurrency markets.

Originally designed for investment styles characterized by a few longer-term positions, the 2% rule is better suited for less volatile instruments than cryptocurrencies. As an active trader, especially when initiating your trading journey, it is prudent to exercise even greater caution. Thus, we shall adjust this rule to the 1% rule.

Under the 1% rule, the guideline stipulates that no more than 1% of your account should be put at risk in a single trade. However, it is crucial to note that this does not imply allocating only 1% of your available capital to every trade. Instead, it ensures that if your trade idea proves incorrect and your stop-loss is triggered, the maximum loss incurred will be limited to 1% of your account.

Identifying Invalidation Points

Having established our account size and account risk, the next step involves determining the position sizing for an individual trade. A fundamental aspect of virtually any trading strategy is identifying where our trade idea becomes invalidated. In trading and investing, losses are an inherent part of the process—a certainty rather than an exception. Trading revolves around probabilities; even the most accomplished traders are not infallible. In fact, some traders may be wrong more often than they are right and still achieve profitability. The key lies in proper risk management, adherence to a trading strategy, and unwavering commitment to it.

Hence, each trade idea must have an explicit point of invalidation. At this juncture, we acknowledge that our initial idea was incorrect and take action to mitigate further losses by exiting the position. On a practical level, this translates to placing our stop-loss order.

Determining the invalidation point depends entirely on the individual trading strategy and the specific market setup. This point can be derived from technical parameters like support or resistance areas. Alternatively, it could be derived from indicators, a break in market structure, or other unique factors.

It is crucial to note that there is no universal approach to setting stop-loss levels. You must discern which strategy best aligns with your trading style and determine the invalidation point accordingly.

Applying the Position Sizing Formula

The calculation of position size incorporates all the necessary components we have gathered thus far. For instance, let's assume we have a trading account worth $5,000 and have established a maximum risk of 1% per trade. Consequently, we cannot exceed a loss of $50 on any single trade. Now, let's consider that our market analysis reveals an invalidation point of 5% from our initial entry. Essentially, when the market moves against us by 5%, we exit the trade, resulting in a $50 loss. In other words, 5% of our position should equate to 1% of our account.

Given the following parameters:

  • Account size: $5,000
  • Account risk: 1%
  • Invalidation point (distance to stop-loss): 5%

We can employ the following formula to calculate position size:

Position size = Account size × Account risk / Invalidation point 

Position size = $5,000 × 0.01 / 0.05 = $1,000

Hence, the position size for this trade amounts to $1,000. By adhering to this strategy and exiting at the predetermined invalidation point, you effectively limit the potential loss. It is important to consider additional factors such as transaction fees and potential slippage, especially when trading low liquidity instruments.

To illustrate further, let's increase the invalidation point to 10% while keeping all other parameters the same.

Position size = $5,000 × 0.01 / 0.1 = $500

With the new invalidation point, the distance from our initial entry to the stop-loss has doubled. Consequently, if we aim to risk the same dollar amount from our account, the position size is halved accordingly.


Position sizing calculation is not contingent upon a random strategy but rather encompasses the evaluation of account risk and identification of trade invalidation points prior to trade execution. Equally crucial to this approach is disciplined execution. Once position size and invalidation points have been determined, it is imperative not to modify them during live trades. The most effective means of mastering risk management principles such as these is through practical application. 

Position Size
Invalidation Point