What multiple position sizing means
Multiple position sizing is a way to size several forex positions (for example, multiple entries toward the same overall idea) using a consistent risk definition. Instead of treating each entry as an unrelated trade, you define how much total risk (or total account exposure) the group is allowed to add, then convert that allowance into position sizes.
A useful distinction is between stable mechanics and variable conditions:
- Stable mechanics: how you translate an assumed risk amount into position sizes using stop distance and units.
- Variable conditions: market movement, bid/ask spreads, commissions, slippage, and execution timing.
Because those variable conditions are not known in advance, any “worked example” is not a prediction. It is a demonstration of math under explicit assumptions.
Worked example with stated assumptions
This scenario uses a simple, transparent risk model. Assume:
- Account balance is 10,000.
- You allow 1.0% total risk for a single overall idea, across all entries. Total allowed loss at stop is 10,000 × 1.0% = 100.
- You split the idea into 2 positions with equal intended contribution, so each position is sized to risk 50 at its own stop.
- Both positions have the same stop distance: 20 pips.
- The pip value per “standard lot” is 10 per pip. (This depends on instrument and quote conventions; here it is an assumed constant for the example.)
- You measure losses from entry to stop using the stated pip distance, and you ignore costs and slippage in the calculation.
Step 1: Compute each position’s required pip budget.
- Allowed risk per position = 50.
- Stop distance = 20 pips.
- Needed “lot factor” = risk ÷ (pip value × pips) = 50 ÷ (10 × 20) = 0.25.
So you would size:
- Position A: 0.25 lots
- Position B: 0.25 lots
Step 2: Check the group risk at stops.
- Loss for A at stop = 0.25 × 10 × 20 = 50
- Loss for B at stop = 0.25 × 10 × 20 = 50
- Total loss at both stops = 50 + 50 = 100
If the assumptions hold, the total loss when both positions reach their respective stop levels equals the defined group risk.
How it works in practice (mechanism summary)
In a live setting, the mechanics usually follow this pattern:
- Choose a group-level risk amount (a fixed percentage or fixed currency amount).
- Decide the allocation rule for multiple positions (equal split, weighted split, or another predetermined rule).
- For each position, compute size from the risk per position and the stop distance.
- Apply a consistent definition of “loss at stop” (for example, entry-to-stop in pips) and keep it aligned across all positions.
Material limitation: if stop distances differ across positions, the simple “equal risk split” changes the lot sizes. For example, if Position B had a 30-pip stop instead of 20, you would compute a different size to keep its risk at 50 under the same pip value assumption.
Limitations and failure modes
Even with correct math, multiple position sizing can diverge from the intended risk because assumptions often break:
- Execution and pricing differences: spreads, commissions, and slippage can make the realized loss larger or smaller than the modeled stop-to-entry movement.
- Correlated outcomes: the idea may cause both positions to be stopped in nearby time, so the total group loss can resemble the “both hit stop” case, not just one leg.
- Model mismatch: the pip value used for sizing may not match the actual contract sizing for the instrument or quote currency; the example assumes a constant 10 per pip per standard lot.
- Stop interpretation: “stop distance” must match how stops are actually placed and triggered (for example, whether stop levels are identical in pips and whether partial fills occur).
A worked example is therefore best viewed as “math under assumptions,” not as a guarantee about real outcomes.
Verification and next question to ask
To independently verify a multiple position sizing calculation, you can:
- Recompute the lot size from the formula: size = risk ÷ (pip value × stop pips). - Sum the per-position risks to confirm the group risk equals the defined allowance. - Replace the assumed pip value with the actual pip value for the specific instrument and account currency used in your environment.