Risk per trade: how to use the 1% rule without misusing it

1. Define what 1% risk actually means

For a $25,000 account, 1% is a $250 planned loss. That number is the trade's budget at the stop, including estimated slippage and round-turn costs. It is not the notional value of the position, cash invested, initial margin or maximum possible loss. A leveraged position can have a large notional value while its planned stop risk is $250—and a gap can still make the realized loss larger.

2. Choose the account base consistently

Current equity is usually the most conservative operational base because it reflects realized results and open profit or loss. Starting balance can overstate the budget after a drawdown. A prop firm's advertised account size can be especially misleading when the actual loss room is only a fraction of that number.

3. Convert the budget into position size

The percentage decides how many dollars may be lost; the stop and product specification decide how many units fit. Place the stop where the thesis is invalidated before calculating size. Otherwise the position-size target can tempt you to tighten the stop artificially and change the trade itself.

If a $250 budget meets a $93.20 loss per MNQ contract, the raw result is 2.68 contracts and the executable result is two. Rounding to three would risk $279.60 and deliberately breach the rule. For CFD lots, round down to the broker's lot step; for shares, use the permitted whole or fractional-share increment.

4. Worked example: 1% is a ceiling, not a target

The planned loss becomes $96.25, or about 0.52% of equity. Two contracts would risk $192.50 and exceed 1%. The unused $88.75 is not an error: discrete contract sizes often make the actual risk lower than the percentage ceiling.

5. Measure what a losing streak does to equity

When the same percentage is applied to current equity, the dollar budget contracts after each loss. Ignoring costs and slippage beyond the budget, equity after n full-risk losses is initial equity × (1 − risk rate)ⁿ. This does not predict streak probability; it shows the mechanical drawdown if the streak occurs.

6. Add open, correlated and daily risk

A per-trade cap does not control the account by itself. Long NQ, long semiconductor shares and long a technology index CFD can share the same downside driver. If all three are sized at 1%, describing the portfolio as 'only 1% risk' is false.

• Sum the remaining stop risk of every open position before adding a trade.
• Group positions by common market, sector, currency or event exposure.
• Set separate ceilings for total open risk, correlated risk and session loss.
• Include the new trade's costs and worst plausible gap scenario in a stress check.
• Reduce or reject the trade when the smallest account limit has insufficient room.

7. Calibrate the percentage from evidence and constraints

The right test is not whether 1% sounds conservative. Estimate the strategy's historical losing streaks, realized slippage, number of simultaneous positions and drawdown tolerance. Then run scenarios above the historical worst case. A limited sample cannot reveal the true worst streak, so leave a margin of safety.

1. Define the maximum account and daily drawdown you can operationally tolerate.
2. Measure realized average and tail losses in risk units, including costs.
3. Stress longer losing streaks and correlated losses than observed.
4. Choose a percentage that remains inside every limit under those scenarios.
5. Reassess only after enough new trades or a material strategy/rule change—not after one win or loss.

8. Pre-trade checklist

• The account base and percentage are defined before the setup appears.
• The stop reflects invalidation and uses a valid tick or price increment.
• Slippage, spread and round-turn costs are included.
• Quantity is rounded down to the tradable increment.
• Open, correlated, daily-loss and drawdown limits still have room.
• The order type and gap risk are understood; the budget is not described as a guaranteed maximum loss.