Direct answer
A Partial Close is when you close only part of an open trading position, leaving the remaining portion still open. A “worked example” explains the mechanics with specific numbers and states every assumption, so you can independently verify how the closed portion’s result is computed and why the remaining portion’s result is separate.
Mechanism or definition
Consider an open position with:
- Total size (for example, 1.00 lot)
- Entry price (the price at which the position was opened)
- Partial Close action (for example, closing 40% of the position)
- Close price (the price at which the partial close is executed)
Stable mechanics (non-market assumptions): the partial close applies to a fraction of the original size. The realized outcome is based on the price move from entry to the close price for only the closed fraction. The remaining fraction continues to be exposed to subsequent price moves, and its eventual realized outcome is calculated later using its then-executed close price.
Variable factors (not assumed as certain): real fill prices can differ from the close price you used in your calculations due to execution quality, slippage, and spread changes. Costs such as commissions or swap/financing can also affect net results, but they are often omitted in simple examples unless explicitly included.
Evidence or example
Below is one worked scenario. It uses simplified assumptions so you can verify the arithmetic.
Assumptions (state explicitly)
- You opened a long position at an entry price of 1.1000.
- Total position size is 1.00 lot.
- You perform a Partial Close of 40% (so you close 0.40 lot and leave 0.60 lot open).
- The partial close executes at a close price of 1.1050.
- You ignore fees, commission, and swap/financing, so calculations reflect only price movement.
- You use the standard idea that profit for a long position increases when price rises.
Step 1: Compute the price move for the closed portion
- Price move = 1.1050 − 1.1000 = 0.0050.
Step 2: Apply the closed fraction
- Closed fraction = 40%.
- Closed size = 1.00 lot × 0.40 = 0.40 lot.
Step 3: Compute realized P/L conceptually
A worked example must be complete enough to check. Since exact pip value per lot depends on contract specifications and account configuration, we keep the result in “per-lot price-move terms”:
- Realized result for the closed portion is proportional to: (closed size) × (price move).
- So realized P/L is proportional to 0.40 × 0.0050 = 0.0020 lot×price (with the sign positive because it is a long and price rose).
Step 4: Separate the remaining portion
After the Partial Close:
- Remaining open size = 1.00 lot × 0.60 = 0.60 lot.
- The remaining portion has not been realized yet. Its final result will depend on later execution prices for when you close the rest.
How to independently verify
To verify your own Partial Close example, repeat the same fraction logic:
- Identify the closed fraction (e.g., 40%).
- Compute the closed size (e.g., 0.40 lot).
- Compute the price move for the closed action (close price − entry price for a long).
- Apply proportionality to confirm the realized result refers only to the closed portion.
Limitations and risks
- Costs and financing can change the net result. If you ignore commissions or swap/financing, your example will not match your account’s net profit or loss.
- Execution quality can break “single-price” assumptions. Real fills can occur at different prices than the close price you used in a calculation due to slippage or changing spreads.
- Unit and fraction mistakes are common failure modes. Confusing “percent of position” with “percent of exposure,” using the wrong lot fraction, or misunderstanding whether the platform treats the fraction in size units or margin units can lead to incorrect expectations.
- Partial closes can behave differently under execution constraints. In some environments, the close may occur in multiple fills, which changes the effective average close price.
- Historical arithmetic does not guarantee future outcomes. Even if your worked example matches a prior situation, future market movement and execution conditions can differ.