Bid-Ask Spread Definition: The bid-ask spread is the difference between the highest price a buyer will pay for an asset (the bid) and the lowest price a seller will accept (the ask). It is the primary cost of trading immediately — every market order pays the spread on entry. On liquid markets like EUR/USD or BTC/USD, the spread can be less than 0.01% of the asset’s price; on illiquid assets, it can exceed several percent.
What Is the Bid-Ask Spread?
No market quote is a single price. Every tradeable asset has two prices at all times: the bid, where buyers are willing to buy, and the ask, where sellers are willing to sell. The spread is the gap between them — and crossing that gap is the cost of executing a trade at the current moment rather than waiting for the market to come to you.
The spread exists because of market makers — participants who continuously post both bids and asks to provide liquidity. By buying at the bid and selling at the ask, market makers capture the spread as compensation for the risk of holding inventory and for being available to trade at any moment. Without market makers, buyers and sellers would need to find each other directly, and the time and uncertainty of that process would make markets far less efficient.
On highly liquid instruments — EUR/USD, BTC/USD, S&P 500 futures — competition among market makers keeps spreads extremely tight. EUR/USD typically trades with a spread of 0.5–1.5 pips (0.005%–0.015%). On small-cap altcoins or exotic forex pairs, spreads of 1–5% are common because fewer market makers compete and the risk of holding inventory is higher. The spread is a direct measure of market liquidity: tighter spreads mean more liquid markets.
How Does the Bid-Ask Spread Work?
Every market order pays the spread immediately. A market buy executes at the ask; a market sell executes at the bid. The moment a market order fills, the position starts with an unrealised loss equal to the spread. To break even, price must move in the trader’s favour by at least the spread amount before the position can be closed at no loss.
Worked example: BTC/USD is quoted at 67,150 (bid) / 67,200 (ask). The spread is $50 — roughly 0.07% of the price. You buy 1 BTC at market, paying $67,200. To break even on a market sell, BTC must rise to at least $67,250 — the $67,200 you paid plus the $50 spread you will pay again on exit. Your effective breakeven is not your entry price but your entry price plus the round-trip spread cost.
The spread is not fixed — it widens and narrows with market conditions. During peak trading hours when volume is high and many market makers compete, spreads are tightest. During off-hours, weekends, or immediately before major news releases, market makers widen spreads or pull their orders entirely to reduce inventory risk. A spread that is 2 pips on EUR/USD during the London session can jump to 10–15 pips in the minutes before a US Non-Farm Payrolls release.
Types of Spreads
Fixed spread — set by the broker and does not change regardless of market conditions. Convenient for budgeting trading costs, but fixed spreads are typically wider than variable spreads during normal conditions because the broker prices in the risk of volatile periods.
Variable spread — fluctuates with real-time market liquidity. Tighter during liquid sessions, wider during news events and low-volume periods. Variable spreads more accurately reflect true market conditions and are narrower on average, but they create uncertainty around execution costs.
Raw spread — the interbank or exchange spread passed directly to the trader, with a separate commission charged per trade. Common on ECN (Electronic Communications Network) brokers. The headline spread appears very tight — sometimes 0 pips — but the commission must be added to calculate the true cost.
Why Is the Bid-Ask Spread Important for Traders?
The spread is a silent tax on every trade, and its impact depends entirely on trading style. A position trader holding for weeks barely notices a 2-pip spread on a 200-pip trade — the cost is 1% of the profit target. A scalper targeting 5-pip gains pays that same 2-pip spread, which represents 40% of the target profit before the position even moves. For high-frequency strategies, the spread is often the single largest cost — larger than commissions, larger than slippage, larger than overnight financing.
Choosing the right instrument and session for a given strategy is inseparable from spread awareness. Major forex pairs during the London-New York overlap offer the tightest spreads in the world. Exotic currency pairs or illiquid crypto altcoins in the same hours carry spreads that make short-term trading economically unviable. A strategy that works on EUR/USD may fail entirely on a pair with five times the spread, even if the price patterns are identical.
Spreads also widen predictably around scheduled events — central bank decisions, CPI releases, Non-Farm Payrolls. Traders who hold positions through these events face not just directional risk but spread risk: the cost of exiting a position spikes precisely when the need to exit quickly is highest. Closing a position before a major release and re-entering after avoids this compounding of costs.
Key Takeaways
- The bid-ask spread is the difference between what buyers will pay and what sellers will accept — every market order pays this spread on execution, starting the position with an immediate unrealised loss equal to the round-trip spread cost
- EUR/USD typically trades with a spread of 0.5–1.5 pips (0.005%–0.015%) during peak hours; small-cap altcoins can carry spreads of 1–5%, making the spread the dominant trading cost on illiquid assets
- Spreads widen during low-volume periods, news events, and market stress — a 2-pip EUR/USD spread during the London session can jump to 10–15 pips in the minutes before a major data release
- For scalpers targeting 5-pip gains, a 2-pip spread consumes 40% of the profit target before the trade even moves — spread awareness is not optional for short-term strategies
- Raw spread accounts with near-zero spreads charge a separate commission per trade — the true cost is spread plus commission, which must be combined to compare accurately against fixed-spread accounts
Why does the spread widen before news events?
Market makers protect themselves from directional risk around scheduled data releases by widening spreads or pulling their orders entirely. If a CPI print surprises markets and price moves 50 pips instantly, a market maker with a 1-pip spread is exposed to significant inventory losses. Widening the spread to 15 pips during the release window reduces that risk.
Is a tighter spread always better?
For most traders, yes — tighter spreads mean lower transaction costs. The exception is raw-spread accounts that charge commissions: a 0-pip spread account with a $5 commission per lot can cost more than a 0.5-pip spread account with no commission, depending on lot size. Always calculate total cost as spread plus commission to compare fairly.
How do I know if a spread is fair?
Compare it to the spreads offered on the same instrument by multiple brokers during the same market hours. Significant deviations from the market average suggest either that the broker is adding a markup to the underlying spread or that their liquidity providers are less competitive. Public aggregators and broker comparison sites track typical spreads for major instruments.
Does the spread affect limit orders?
Yes, indirectly. A buy limit order fills when the ask reaches your limit price — which means the bid at that moment is your limit price minus the spread. If you set a buy limit at 67,000 and the spread is $50, the bid is 66,950 when your order fills. For tight-target trades, this 50-point difference affects whether subsequent limit sells execute at your intended profit target.
