What is a Worked Example of Spread By Pair?

Direct answer

A worked example of spread by pair shows, step by step, how you translate a quoted spread for a specific currency pair into an estimated transaction cost for a chosen trade size. It separates stable mechanics (how spreads relate to bid and ask) from variable conditions (how wide spreads are at the moment, how execution happens, and what extra fees apply). You can independently verify the calculation because every assumption is stated.

Mechanism and definition

A spread is the difference between the ask price (the price you pay to buy) and the bid price (the price you receive to sell). For a currency pair quoted in the market, the spread by pair means: the spread value can differ across currency pairs because pricing, liquidity, volatility, and market structure are not the same.

A worked example typically needs these inputs:

• Pair and quote convention (how the pair is written).
• Spread size expressed in quote price units (for example, “0.0002” in the pair’s quote format).
• Trade size (for example, number of base units).
• A method to estimate cost: often approximated as spread/half-spread logic (you pay the ask instead of the mid) for an immediate round-trip cost estimate.

Important clarification: “spread cost” is not the same as “total trading cost.” Commissions, financing/rollover charges, and slippage can add or change the realized cost.

Evidence or worked example (scenario with explicit assumptions)

Assume a simplified scenario for a currency pair with a quote convention where the spread can be treated directly in the quote price units.

Assumptions

1. Pair: one currency pair (name is not required for the math shown here).
2. Quoted spread: the provider quotes a spread of 0.0002 in the pair’s quote price units.
3. Trade size: you execute a position of 100,000 base units.
4. Cost model: you estimate immediate transaction impact using the spread as the difference you effectively pay versus a mid reference. No commission is included.
5. Execution: you receive prices exactly at the quoted bid/ask at trade time.
6. No slippage: order fills occur without additional unfavorable price movement.

Numerical calculation

• Spread (ask − bid) = 0.0002
• In this simplified model, the immediate “spread distance” applied to the trade is proportional to trade size.

Let estimated spread cost in quote currency units be:

• estimated cost = spread × trade size
• = 0.0002 × 100,000
• = 20

So, under these assumptions, the spread creates an estimated cost of 20 quote-currency units for the one-direction entry pricing impact.

Round-trip note (optional check)

If you estimate a rough round-trip impact (buy then later sell), a common simplification is to apply spread-related cost twice: once on entry and once on exit. Using the same simplified model and ignoring other costs, that could be about 40 quote-currency units. This is still an approximation because the exit spread may differ and execution may occur at different bid/ask values.

Limitations and risks (what can break the example)

1. Spread size is variable: spreads can widen or tighten with market conditions. A worked example uses one assumed spread and cannot reflect future changes.
2. Provider-specific definitions: different providers can display spreads using slightly different conventions (for example, whether it is shown as raw bid/ask difference at the moment, or averaged/rounded values). That affects the inputs you should use.
3. Extra costs: commissions, swaps/financing, and other fees may exist. The example above assumes none; real total cost can be higher or structured differently.
4. Execution quality and slippage: even if you start from quoted bid/ask prices, real fills can occur at worse prices, especially during volatility. Slippage changes the realized cost.
5. Currency conversion complexity: if your account currency differs from the quote currency, you may need additional conversion steps. A worked example must state how conversion is handled; otherwise the numerical result is not directly verifiable.

Verification and next question

To verify the calculation independently, you should be able to point to the exact inputs used: the quoted spread value, the trade size, the quote convention, and the cost model assumptions (for example, whether you treat spread as a proportional immediate cost and whether you estimate entry-only or round-trip).