OptiNod Academy

Position Sizing: How Much to Risk on Each Trade

Account survival comes down to how much you risk on one trade. Size is calculated from the stop distance, and correlated positions should be treated as one bet.

> Account survival is determined by how much you risk on a single trade. The strength of an entry signal has little to do with it. Position size is calculated backward from the *stop distance*.

In the previous two articles, we saw that 1R comes from the stop-loss level. Now it is time to turn that 1R into actual dollars and position size. Position sizing is the step where you decide how much of your account to risk on one trade. Whether the account survives over time is decided here. The accuracy of your entry signals has little to do with it.

A common approach is to size positions based on conviction: "This one is high confidence, so go bigger," or "The signal is weak, so keep it small." Another approach is to use the same quantity for every trade, such as always buying 0.1 BTC. Both methods make the amount lost on each trade, or 1R, inconsistent.

Conviction does not guarantee a higher win rate, and using a fixed quantity means you are risking a different amount each time because stop distance varies by asset and setup. If you use the same quantity on a trade with a 2% stop and another with a 9% stop, the second trade loses 4.5 times more at the stop. When the loss on a single trade is not controlled, even a positive-expectancy system can be pushed into an unrecoverable drawdown during a losing streak.

With the same quantity, a wider stop means a larger loss on one trade

Calculate Position Size From the Stop Distance

The sizing formula is one line: divide the amount you are willing to risk on the trade, or 1R, by the stop distance. Suppose your account is $10,000 and you set 1R at 1% of the account, or $100. If you buy BTC at $60,000 and place the stop at $58,500, the stop distance is $1,500.

Position size is $100 divided by $1,500, or about 0.0667 BTC. In notional terms, that is roughly $4,000. If the stop is hit, you lose exactly $100, or 1% of the account.

When the stop distance changes, position size changes automatically. With the same account, if the stop distance is narrower at $750, size increases to about 0.133 BTC. If the stop distance is wider at $3,000, size falls to about 0.033 BTC. No matter how wide or narrow the stop is, the loss at the stop remains $100. That is the result of first asking, "How much can I afford to lose on this trade?" and working out the units from there.

Define 1R as a Fixed Percentage

It is better to set 1R as a fixed percentage of the account, such as 1%, instead of a fixed dollar amount such as always $100, and there is a clear reason for this. If the account declines, 1% declines with it, so the amount risked automatically gets smaller during a losing streak. If the account grows, the amount risked grows as well, allowing gains to compound.

A fixed dollar risk removes that automatic adjustment. If the account has been cut in half but you still risk the original dollar amount, you are now risking twice as much in percentage terms, which makes recovery harder. For most traders, 1R is best kept between 0.5% and 2% of the account. In volatile crypto markets, the lower end of that range is usually preferable. At 1%, even a long losing streak only reduces the account gradually, leaving it intact.

Losses Are Asymmetric

Loss and recovery are not symmetric. If an account falls 10%, it needs a little over 11% to get back to breakeven. The gap widens quickly as losses grow.

  • A 10% loss takes about an 11% gain to recover.
  • A 20% loss requires a 25% gain.
  • A 50% loss requires a 100% gain, meaning the remaining capital must double.
  • A 75% loss requires a 300% gain.

That is why the first goal of position sizing is to avoid large losses. Making large profits comes second. A trader risking 1% per trade loses only about 10% of the account after ten straight losses. A trader risking 25% per trade reaches a nearly unrecoverable state after only four losses. Small sizing can feel slow, but avoiding unrecoverable loss is the first condition for long-term survival.

The gain needed to break even climbs steeply as the loss deepens

Even Positive Expectancy Can Fail With Oversizing

Even a positive-expectancy system can go bankrupt if the position size is too large. This may feel counterintuitive, but it is explained by the concept of risk of ruin. As the percentage risked per trade increases, normal losing streaks become more likely to drag the account close to zero.

Consider a system with a 50% win rate and a 2:1 reward-to-risk ratio, which clearly has positive expectancy. If it risks 1% of the account on each trade, the system can grow steadily over time. But if the same system risks 40% of the account on each trade, only three or four consecutive losses can put the account in an unrecoverable position. Positive expectancy is realized only when the bet size is small enough and spread across enough trades. In a single oversized bet, luck controls the outcome. Expectancy barely matters.

Same positive edge: small risk compounds, oversizing busts on a losing streak

The Kelly Criterion and Half Kelly

The Kelly Criterion is a formula that answers the question of how much to risk per trade. It calculates the betting fraction that maximizes long-term growth using win rate and reward-to-risk ratio. In theory, this fraction produces the fastest account growth.

For example, with a 50% win rate and a 2:1 reward-to-risk ratio, the Kelly formula gives a position size of 25% of the account. That means risking one quarter of the account on a single trade, exposing you directly to the oversizing risk discussed above.

At full Kelly, drawdowns around 50% are normal. Most people cannot tolerate that volatility and abandon the system midway. Kelly also assumes that win rate and reward-to-risk are known precisely. In live trading, those numbers are only estimates, and they are often overstated.

That is why practitioners usually do not use the full Kelly value. Even half Kelly, or 12.5% in this example, is too large for most traders. Many use less than half Kelly, or simply use the fixed 0.5% to 2% risk range discussed earlier. Growth is a little slower, but volatility is much lower, which makes it possible to stay with the system.

Correlated Positions Are One Bet

Even if each position is sized at 1%, holding five correlated positions at the same time effectively means risking 5% on one idea. This is especially important in crypto. Most altcoins move in the same direction as BTC, and during sharp selloffs they often drop together.

August 5, 2024, offers a clear example. That day, BTC fell 7% from the previous close, and its intraday low was 16% below that close. On the same day, ETH fell 10% on a closing basis and about 22% at the intraday low. SOL's intraday low was about 20% below the previous close.

An account that thought it was diversified by risking 1% each on five altcoins could lose well over 5% in one day as all five positions collapsed in the same direction. Because alts often move more than BTC, an altcoin basket that looks diversified is closer to a single leveraged bet on BTC. Correlated assets should be managed together as one 1R.

So in addition to sizing each position at 1R, you also need a cap on the combined open risk across all positions. A common rule is to limit total potential loss to 5% to 6% of the account. If 1R is 1%, you can hold five or six low-correlation positions at the same time, but strongly correlated positions should be counted together. It is safer to treat five altcoins as one risk bucket.

Five correlated positions act as one bet and must share a single 1R

Two Ways to Keep 1R Consistent

First, make pre-trade sizing a habit. Define the entry and stop first, divide the 1R amount by the stop distance to calculate size, and enter only with that size. If this sequence breaks, and you choose size first or increase it because of conviction, 1R becomes unstable and expectancy calculations lose meaning.

  • Account and 1R: Account size is $10,000, and 1R is fixed at 1% of the account, or $100.
  • Trade setup: Entry is $60,000, stop is $54,600, and stop distance is $5,400, or 9%.
  • Position size: $100 divided by $5,400 is about 0.0185 BTC, or roughly $1,100 in notional value.
  • Result: Trades with narrower stops get larger size, trades with wider stops get smaller size, and the amount lost at the stop is always $100 regardless of the trade.

Second, recalculate 1R whenever the account grows or shrinks by a meaningful amount. If risk is set as a fixed percentage, the dollar value of 1R must change as the account balance changes. Many traders keep using the original 1R amount after the account grows, causing the risk percentage to shrink over time. Others keep using an oversized 1R after the account declines, making recovery harder.

Across these three articles, expectancy, stops, and sizing all converge into one sentence: decide how much you are willing to lose first, confirm that the amount is small enough for positive expectancy to play out, and only then enter the trade.