What is bid ask spread?
Bid Ask Spread is the difference between two prices in a forex quote: the bid and the ask.
- Bid: the price at which someone (typically your counterparty via the platform) is willing to buy the currency pair from you.
- Ask: the price at which someone is willing to sell the currency pair to you.
- Spread: usually expressed as ask − bid (or as “points/pips” depending on the quote convention).
The key idea is mechanical: you do not transact at a single mid-market price. When you buy, you typically pay the ask; when you sell, you typically receive the bid. That means the spread acts like an immediate trading cost.
How does bid ask spread work in forex?
Forex platforms display quotes that include both a bid and an ask to reflect supply and demand at that moment. If the bid and ask are close together, the spread is small; if they are far apart, the spread is larger.
A simple example (assumptions stated): suppose a forex quote shows bid = 1.1000 and ask = 1.1002.
- The spread is 1.1002 − 1.1000 = 0.0002.
- If you buy right then, you typically enter around 1.1002.
- If you sell right then, you typically exit around 1.1000.
This is distinct from the mid price (often thought of as the midpoint between bid and ask). The mid price is a reference, not the price you usually transact at.
Spread vs. adjacent quote ideas
It helps to separate spread from concepts that people often mix together:
- Spread (cost/time-of-quote): the bid–ask gap shown in a quote.
- Volatility (market movement): how much prices move over time; volatility can cause spreads to widen.
- Slippage (execution difference): the difference between the expected execution price and the actual one. Even with a quoted spread, your fill can occur at a slightly different price if conditions change.
One calculation you can verify
If you have both bid and ask values from the same moment, you can compute the spread directly as ask − bid using your quote’s decimal places or point/pip conversion. This does not guarantee your total trading cost, but it gives a quote-level measure.
Relevant limitations and risks
Bid Ask Spread is not a fixed number. Several material limitations affect how you should interpret it:
- Market conditions change: liquidity and order-book depth can vary. During fast moves, spreads can widen quickly.
- Provider/platform quote rules can differ: different platforms may display spreads differently (for example, varying quote update frequency or quote conventions). The same “spread” label may represent different practical costs.
- Realized cost may include more than spread: execution costs can also be affected by commissions, financing/holding charges, and how fills occur. Spread alone often does not capture the full cost.
- Spread can be temporarily misleading: a spread you observe at one instant may not match the spread at the moment your order is filled.
A common failure mode is assuming that the quoted spread fully determines profitability or that a smaller spread always means easier trading. While a smaller spread usually indicates less immediate cost in many situations, your realized outcome still depends on execution timing, price movement, and other costs.
Verification and next question to ask
To independently verify your understanding, compare bid and ask values displayed on your platform at the same timestamp and compute ask − bid. Then ask:
- Does your platform execute buys closer to the ask and sells closer to the bid?
- Under volatile or illiquid conditions, does the observed spread widen?
If you want to go deeper, focus on how bid ask spread matter in forex and how bid ask spread work in forex using the quote behavior you observe rather than relying on a single number.