What Formula Does a Lot Size and Pip Value Use?

Direct answer

A lot size and pip value combination is used to turn “how many lots” you trade into an estimated money change per pip (the smallest quoted price increment you are treating as a pip). The core idea is simple: you convert your position size into units, then scale by the pip size to get the value of one pip move.

There are two related formulas people often mix:

Position size in units (from lots).
Pip value in money terms (from units, pip size, and currency conversion assumptions).

Because brokers and platforms can define “pip” and quoted pip size differently by instrument, you must state the assumptions you use for pip size and conversion.

Mechanism and definitions (what the inputs mean)

Lot size (lots → base units)

In many retail forex contexts, 1 standard lot corresponds to 100,000 units of the base currency (the first currency in the pair). A common educational mapping is:

Standard lot (100,000 units)
Mini lot (10,000 units)
Micro lot (1,000 units)

This mapping is a convention used widely in forex pricing education. Some providers may vary in how they label sizes, so treat “units per lot” as an input you verify on the specific platform contract specification.

Pip size (price increment)

A pip is a price step you treat as the basic measure of movement. For many major pairs quoted to 5 decimals, people often treat:

1 pip = 0.0001 price movement for pairs where the “pip” is the 4th decimal place.
For JPY pairs, “pip” is often tied to 0.01 price movement.

However, the exact pip size you should use depends on the instrument quoting format and the platform’s pip convention. Therefore, pip size is an explicit assumption in any calculation.

Base and quote currencies (why conversion may be needed)

A forex pair like BASE/QUOTE means the quoted price tells you how much QUOTE currency you pay/receive for 1 unit of BASE.

If your account currency matches QUOTE, the conversion to account money may be direct.
If your account currency is neither BASE nor QUOTE, you typically need a conversion rate from QUOTE to account currency.

So the pip value formula may include a currency conversion step, even if the first part is instrument mechanics.

The main formulas

1) Convert lot size to base units

Let:

L = number of lots
U_per_lot = base units per 1 lot (e.g., 100,000 for a standard lot)

Then:

Base units (U) = L × U_per_lot

Example assumption: if L = 0.50 and U_per_lot = 100,000, then U = 50,000 base units.

2) Convert a pip move into a pip value in quote terms

Let:

Ppip = pip size in price terms (e.g., 0.0001 or 0.01)
Price = current quoted price for BASE/QUOTE used for conversion logic (when needed)

For a straightforward educational model, the value of 1 pip move for a position is often expressed using:

Pip value (in QUOTE currency) ≈ (U × Ppip) / Price

This form reflects that a move of Ppip changes the value in QUOTE relative to the BASE notional, and division by Price accounts for the pair relationship. In some cases (for example, when pip value is already defined in a consistent way by the platform), the platform may present pip value directly, effectively skipping parts of this derivation.

If your pip value target is in account currency, add a conversion rate if required:

Pip value (in account currency) = Pip value (in QUOTE) × FX_convert

Where FX_convert is the rate converting QUOTE currency into account currency.

3) Alternative “pip value per unit” viewpoint (often used for checks)

You can also compute a pip value per base unit:

Pip value per base unit ≈ Ppip / Price (in QUOTE terms) Then multiply by units:
Pip value ≈ U × (Ppip / Price)

This is mathematically the same as (U × Ppip) / Price.

Evidence or example: full walkthrough with explicit assumptions

Example A: Standard pip assumption (non-JPY style)

Assumptions (you must adapt to your instrument):

Pair is BASE/QUOTE quoted like 1.23456, where 1 pip = 0.0001
Standard lot: 100,000 units
Position: L = 0.20 lots
Base/quote price used in the calculation: Price = 1.23456

Step 1: Units

U = 0.20 × 100,000 = 20,000 units

Step 2: Pip move size in price terms

Ppip = 0.0001

Step 3: Pip value in QUOTE (using the common model)

Pip value ≈ (U × Ppip) / Price
Pip value ≈ (20,000 × 0.0001) / 1.23456
Pip value ≈ 2 / 1.23456
Pip value ≈ 1.62 QUOTE currency per pip (rounded to two decimals for readability)

If your account currency is QUOTE, this is also your account-currency pip value. If not, apply the conversion you assume.

Example B: JPY-style pip assumption

Assumptions:

Pip size for the JPY pair is Ppip = 0.01
Standard lot: 100,000 units
L = 0.10 lots ⇒ U = 10,000 units
Price = 147.25

Pip value in QUOTE:

Pip value ≈ (10,000 × 0.01) / 147.25
Pip value ≈ 100 / 147.25
Pip value ≈ 0.68 QUOTE currency per pip (rounded)

Rounding and units

Pip value is typically reported with 2 decimals in the account’s currency, but you should keep extra precision during calculation and round only at the end.
If a platform reports pip value per pip in a different way (for example, per “tick” or per “pipette”), that changes Ppip or the interpretation of the price increment.

Limitations and risks (material failure modes)

Wrong pip definition If you use 0.0001 when the instrument’s pip convention is different (or the platform uses 5-decimal “pipettes” for pricing), your pip value can be off by a factor of 10.
Wrong units-per-lot convention If the provider’s contract specification defines a different U_per_lot for the instrument type (or you are using an account with different contract sizing), your position-to-units conversion becomes wrong.
Currency conversion assumption mismatch The formula (U × Ppip) / Price gives pip value in QUOTE currency in many educational setups. If your account currency is different and you do not apply the correct conversion rate you assumed, the final pip value will not match what the platform displays.
Using an inconsistent Price Some models use the current price for conversion. If you use a stale price or a different reference price than the platform uses, the pip value estimate can differ.