Risk management

The 3-5-7 Rule in Trading: What It Is and How to Apply It

Astron Team · 09/24/2026 · 6 min read

Most traders don't lose money by picking the wrong assets, but by risking too much on each trade and not having a clear limit for the total exposed at the same time. The 3-5-7 rule is a simple way to organize these limits into three easy-to-remember numbers, creating a risk management structure that any beginner can apply without complicated spreadsheets.

This article explains what each of the rule's three numbers means, how to calculate them in practice, and why this discipline tends to weigh more on the final result than the choice of strategy itself.

The first number: 3% maximum risk per trade

The rule's first pillar defines how much you're willing to lose on a single trade, if the stop is hit: at most 3% of the account's total capital. This percentage refers to the amount lost if the price hits the stop, not the total size of the open position.

To calculate position size based on this limit, use the formula: position size = (account capital x 0.03) ÷ (entry price − stop price). A practical example: with a R$ 10,000 account, the maximum risk per trade is R$ 300. If an asset costs R$ 50 and the technical stop is at R$ 47 (a distance of R$ 3), the maximum position would be R$ 300 ÷ R$ 3 = 100 units, which represents R$ 5,000 invested, even with risk limited to R$ 300.

Why 3% and not more

The logic is statistical: with 3% risk per trade, an extreme streak of 10 losses in a row would leave the account with about 74% of the original capital, a tough scenario, but recoverable. With 10% risk per trade, the same losing streak would practically wipe out the account.

The second number: 5% total simultaneous exposure

The second pillar limits how much capital can be at risk at the same time, adding up all open trades. This avoids the correlation problem: if you open three different trades, each risking 3%, but all in assets that tend to move together (for example, three stocks in the same sector), the real combined risk can exceed 9%, even if each individual trade looks within the limit.

The rule suggests keeping this combined risk from open trades at no more than 5% of total capital, which naturally limits how many positions you can hold at the same time, especially in correlated assets.

The third number: a target of 7% or more on gains

The third pillar deals with the relationship between risk and expected return: winning trades should aim for a gain of at least 7%, or a ratio equivalent to the maximum loss taken. If the risk per trade is 3%, aiming for returns of 7% or more guarantees a favorable risk-reward ratio, around 1 to 2.3.

With this ratio, even a trader who wins less than half the time can end up with a positive overall result. Suppose 40 trades, with a 45% win rate: 18 winners gaining 7% and 22 losers losing 3%. The combined result would be (18 x 7%) − (22 x 3%) = 126% − 66% = 60% accumulated gain in risk percentage taken, an example of how risk-reward math compensates for a win rate below 50%.

• 3%: maximum accepted risk per individual trade.
• 5%: maximum total risk combining all open positions.
• 7%: minimum profit target on winning trades.
• Discipline in following all three numbers matters more than any single number alone.

How to apply the 3-5-7 rule day to day

Before opening any trade, calculate the position size based on the 3% limit, check that the combined risk of already open positions doesn't exceed 5%, and only enter trades whose potential profit target respects a ratio of at least 7% gain against the risk taken.

It's worth remembering that the 3-5-7 rule doesn't guarantee profit or eliminate the risk of loss: it just structures the size of your bets so that a bad streak, which will eventually happen with any strategy, doesn't jeopardize the account's survival. Trading involves real risk of capital loss, and no management system changes that reality.