Bid-Ask Spread
Key Takeaways
- The bid-ask spread is the difference between the highest bid price and the lowest ask price
- It represents a hidden transaction cost — you buy at the ask and sell at the bid
- Tight spreads indicate high liquidity; wide spreads indicate low liquidity
- Market makers profit from the bid-ask spread
Definition
The bid-ask spread is the difference between the highest price a buyer is willing to pay for a security (the bid) and the lowest price a seller is willing to accept (the ask or offer). It is a fundamental concept in trading that represents the cost of executing an immediate transaction.
When you buy a stock using a market order, you pay the ask price. When you sell, you receive the bid price. The spread between these two prices is essentially a transaction cost borne by the investor. For example, if a stock has a bid of $50.00 and an ask of $50.05, you would pay $50.05 to buy and receive $50.00 to sell — the $0.05 spread is an immediate cost.
Market makers and other liquidity providers earn their profit from the bid-ask spread. They continuously quote bid and ask prices, buying from sellers at the bid and selling to buyers at the ask, pocketing the difference. The competition among market makers keeps spreads tight in liquid markets.
How It Works
The bid-ask spread is determined by supply and demand dynamics, trading volume, market volatility, and the number of market participants. Highly liquid stocks like Apple (AAPL) or Microsoft (MSFT) may have spreads as tight as one cent, while illiquid small-cap stocks or penny stocks can have spreads of 5-10% or more.
Spreads tend to widen during periods of high volatility, before major news announcements, during pre-market and after-hours trading, and for stocks with low trading volume. Spreads narrow when there are many active buyers and sellers and the market is calm.
The percentage spread provides a more meaningful comparison across different stock prices: Percentage Spread = (Ask - Bid) / Ask × 100. A $0.01 spread on a $200 stock (0.005%) is much less significant than a $0.01 spread on a $1 stock (1%).
Example
Compare two stocks: Apple (AAPL) trades with a bid of $192.50 and ask of $192.51, a spread of just $0.01 (0.005%). Buying 1,000 shares costs only $10 in spread. Meanwhile, a small-cap biotech stock trades with a bid of $3.50 and ask of $3.65, a spread of $0.15 (4.3%). Buying 1,000 shares costs $150 in spread alone — 15 times more than the Apple trade despite a much smaller total investment. This illustrates why trading costs are significantly higher for illiquid stocks.
Why It Matters
The bid-ask spread is a real but often overlooked cost of trading. Active traders who make frequent transactions can see significant returns eroded by wide spreads. Understanding the spread is essential for choosing appropriate securities to trade and evaluating true transaction costs.
For long-term investors making infrequent trades in liquid stocks, the bid-ask spread is a minor concern. For day traders and swing traders, spread costs can meaningfully impact profitability. Traders should always check the spread before placing an order and consider using limit orders to avoid paying the full spread.
Advantages
- Indicates the liquidity and trading activity of a security
- Competitive spreads reduce transaction costs for investors
- Provides immediate price discovery information
- Narrow spreads facilitate efficient, low-cost market participation
Limitations
- Represents a hidden cost that many investors overlook
- Spreads can widen dramatically during volatile or illiquid conditions
- Displayed spreads may not be available for large order sizes
- Does not capture other transaction costs like commissions or market impact
Frequently Asked Questions
Related Terms
Browse more definitions in the financial terms glossary.