Direct answer
Pip based position sizing is a way to choose a trade size by starting with how much loss you want to limit (for example, a fixed amount in account currency) and then converting that loss limit into a number of units or lots using the instrument’s pip value and the planned stop distance measured in pips. The core idea is: if the price moves a given number of pips against you, the position size should produce approximately the chosen monetary loss.
This article explains the mechanism, the inputs you must define, what outputs you obtain, and the sequence of steps. It does not assume any real-time prices, and it does not guarantee results.
Mechanism and definitions
What “pips” mean in forex
A pip is the standard unit used to describe small price changes in many forex markets. For many currency pairs, one pip corresponds to a fixed decimal move in the quoted exchange rate (for example, moving from 1.1000 to 1.1001 is commonly described as a one-pip change). Some pairs and quoting conventions can use fractional pips or different decimal structures, so “pip size” must be aligned with the instrument’s stated pip definition.
What “pip value” means
The pip value is the monetary value of a one-pip move for a specific position size. For pip based sizing, you need the pip value expressed in your account currency (or a currency you can convert using stated assumptions). Pip value depends on:
- the instrument’s contract specification (lot size / contract size)
- the position size (lots/units)
- the quote structure and whether the account currency matches the pair currencies
- the conversion rate used if your account currency is not the quote or base currency
What “position size” represents
In practice, position size is often expressed as lots (e.g., 1.00 lot) or as units (e.g., number of currency units) depending on the broker/platform. Pip based sizing maps the monetary risk into one of these size measures.
The stable calculation idea
A commonly used risk-based model is:
- Choose a risk amount R in account currency (the amount you intend to lose if the stop distance is fully reached).
- Choose a stop distance D in pips (the planned adverse move measured from entry to the stop level, in pips).
- Determine pip value V in account currency per one pip for a position size of your chosen unit baseline (often per 1.00 lot, or per 1 unit depending on how V is defined).
Then the required position size S is derived from the relationship:
- total loss at stop ≈ D (pips) × V (account currency per pip, for the chosen position size baseline) scaled by S
The exact algebra depends on how V is defined (per lot vs per unit). What matters for independent verification is that your pip-value definition matches your contract specification and your account currency assumption.
Evidence or example (with explicit assumptions)
Because there are no live prices or broker-specific contract details here, the example below uses explicit, simplified assumptions to show the sequence.
Assumptions for the example
- Your account currency is USD.
- The instrument’s pip value is computed using the platform’s contract details and quote conventions.
- You set a stop distance of D = 20 pips.
- You choose a risk amount of R = $50.
- You compute pip value V such that V = $2.50 per pip for one standard lot.
If your pip value is defined per standard lot, the position size in lots is:
- S (lots) = R / (D × V)
- S = 50 / (20 × 2.50) = 50 / 50 = 1.00 lot
What the output tells you
The output is a trade size (1.00 lot in this example) that is consistent with the chosen stop distance and the pip-value assumption. If you later change D (for example, use a smaller stop measured in pips), the calculated size changes inversely.
Step-by-step sequence
- Define risk R: a monetary amount in your account currency.
- Define stop distance D in pips: the adverse move you plan to associate with the stop level.
- Compute pip value V for your instrument and your account currency assumptions.
- Compute position size S by rearranging total-loss = D × V × size-scaling.
- Sanity-check units: ensure “pip,” “pip value,” and the position-size scaling factor all use compatible definitions.
Limitations and risks (material failure modes)
Pip based position sizing is only as accurate as its inputs and its mapping from pips to money. Even when the basic math is correct, several limitations can break the intended risk control.
1) Pip value miscalculation
If you use an incorrect pip definition (wrong decimal structure), wrong contract size, or the wrong currency conversion assumption when your account currency is not aligned with the pair’s currencies, the pip value V can be wrong. A small pip-value error scales directly into the calculated position size.
2) Realized entry and stop may differ from the planned levels
The model assumes that the stop corresponds to the planned pip distance D from the actual executed entry. In reality, execution prices can differ from reference prices, especially when spreads widen or liquidity changes. This can change the realized pip distance and therefore the realized loss.
3) Costs and spreads are not automatically included
Some pip based models consider only price movement expressed in pips. Trading costs such as spread, commissions, or financing charges (for holding positions) may not be captured in a simple “pip distance × pip value” calculation. If costs are excluded, the actual monetary outcome at the stop can be higher than the risk amount R.
4) Breaks when “pip” is not the correct measurement
Some trading environments, instruments, or platforms may use fractional pip conventions or different quoting formats. If your D is measured in a pip convention that does not match the instrument’s pricing increments, the mapping from D to monetary loss becomes inconsistent.
5) Historical relationships do not imply future control
Even if a sizing method worked historically under certain market behavior, it does not establish that future execution conditions, costs, or volatility will produce the same relationship between planned pips and realized outcomes.
Verification and next questions
To independently verify pip based position sizing, you can check the full chain of definitions and unit consistency:
- Confirm the instrument’s pip definition and pip size.