Spreads in Extended Hours
The bid-ask spread—the difference between the price at which buyers are willing to purchase (bid) and the price at which sellers are willing to sell (ask)—is one of the most visible and consequential differences between regular and extended-hours trading. A stock that trades with a one-cent spread during regular hours might have a fifty-cent or larger spread in after-hours. This widening of spreads is the most direct way that extended-hours trading costs traders and investors real money. Understanding why spreads widen, how to predict spread width for different stocks, and how to minimize spread impact on executed trades is essential for anyone trading outside regular market hours.
Quick definition: Bid-ask spreads in extended-hours trading refer to the difference between the best bid and ask prices, which typically widen 5 to 20 times wider than spreads during regular trading hours due to lower volume, fewer market makers, and greater inventory risk.
Key Takeaways
- Bid-ask spreads in extended hours are typically $0.05 to $0.50 for large-cap stocks and $0.50 to $2.00 or wider for smaller stocks, compared to $0.01 to $0.03 in regular hours.
- Spreads widen in extended hours primarily because fewer market makers are willing to provide liquidity, and those that do require higher profit margins to compensate for risk.
- Inventory risk (the risk that a market maker holds shares overnight and the price gaps against them) is a major driver of wider spreads in extended hours.
- Bid-ask spreads cost traders and investors directly—a round-trip trade incurs a cost equal to the full spread multiplied by shares traded.
- Spread width varies by stock quality, time of day, and volatility, with mega-cap stocks having tighter spreads and small-cap stocks having extremely wide spreads in extended hours.
Why Spreads Widen in Extended Hours
The fundamental reason spreads widen in extended hours is the combination of lower volume, fewer market makers, and higher inventory risk. During regular hours, thousands of market makers and trading firms are actively competing to provide liquidity. This competition drives spreads tighter as market makers undercut each other to win order flow. The tight spreads mean market makers profit through high volume—executing many small-profit trades per second adds up to substantial daily profit.
In extended hours, the number of active market makers declines sharply. Many market makers operate only during regular hours because the lower volume in extended hours doesn't justify the infrastructure costs. Those market makers that do operate in extended hours limit their presence to the largest, most liquid stocks. For anything below mega-cap stocks, market maker participation is minimal or entirely absent. With fewer competitors providing liquidity, those market makers who do operate in extended hours can charge wider spreads. The lack of competition means they can widen spreads without fear of being undercut.
Inventory risk provides another major driver of wider spreads. When a market maker buys shares at the bid (say, buying 10,000 shares at $50), they hold those shares and hope to sell them at the ask ($50.10) to capture the $0.10 spread. However, overnight inventory (shares held through the overnight period) carries substantial risk. If a market maker buys shares at $50 in after-hours and holds them overnight, the stock could gap down to $48 when the regular session opens the next day due to overnight news or international market weakness. The market maker faces a $2 per-share loss—a $20,000 loss on 10,000 shares.
To compensate for this overnight inventory risk, market makers widen spreads in extended hours. A fifty-cent spread in after-hours might sound extreme, but from a market maker's perspective, a fraction of that spread goes toward compensating them for the risk of overnight gaps. If gaps occur on average 20% of the time with an average magnitude of $1, then expected overnight inventory loss is $0.20 per share. A market maker needs at least that much spread to break even on average.
Additionally, in extended hours with low volume, market makers know that if they buy shares, they might need to hold them for a significant time before a seller comes along willing to buy at the ask. During that holding period, market risk exists. If a stock is moving (prices changing rapidly), a market maker might be forced to hold shares at a loss while waiting for a buyer. To compensate, they widen spreads.
Bid-Ask Spread Mechanics
Understanding how bid-ask spreads work is essential to understanding their cost. When you submit a market order to buy, you execute at the ask price (the price at which someone is willing to sell). When you submit a market order to sell, you execute at the bid price (the price at which someone is willing to buy). The spread is the difference between these two prices.
For example, if a stock has a bid of $100 and an ask of $100.50, the spread is $0.50. If you buy 1,000 shares at the ask ($100.50) and then immediately sell at the bid ($100), you've lost $0.50 per share, or $500 total on the 1,000-share round-trip trade. This spread cost is unavoidable—you cannot execute a market order at a better price than the worst price available in the market (this is actually the definition of a market order).
The spread works in the market maker's favor. The market maker posts a bid at $100 (willing to buy at this price) and an ask at $100.50 (willing to sell at this price). When a buyer arrives, they buy at $100.50. When a seller arrives, they sell at $100. The market maker buys low ($100) and sells high ($100.50), capturing the $0.50 spread. This profit motivates market makers to continuously provide quotes. However, in extended hours with wide spreads, every transaction incurs a much larger cost.
Spread Width by Stock Category
Bid-ask spreads in extended hours vary dramatically by stock category. Understanding these patterns helps traders assess execution costs before trading.
Mega-cap stocks (market capitalization over $100 billion) such as Apple, Microsoft, Google, Amazon, and Tesla often have extended-hours spreads of only $0.05 to $0.15, nearly as tight as regular-hours spreads. These stocks attract market maker participation even in extended hours because their large trading volumes and global ownership mean that sufficient volume exists in extended hours to justify market maker participation. Additionally, mega-cap stocks have less overnight gap risk relative to their price—a stock trading at $190 that gaps $2 overnight is a 1% gap, while a stock trading at $50 that gaps $2 overnight is a 4% gap. The percentage gap risk is lower for mega-cap stocks, allowing market makers to charge tighter spreads.
Large-cap stocks (market capitalization $10 billion to $100 billion) typically have extended-hours spreads of $0.10 to $0.30. These stocks still have reasonable participation from market makers, but less than mega-cap stocks. Examples include major bank stocks, established tech companies outside the mega-cap tier, and large industrials.
Mid-cap stocks (market capitalization $2 billion to $10 billion) typically have extended-hours spreads of $0.20 to $0.75. Market maker participation is limited, and gap risk is higher relative to stock price. These stocks are actively traded in regular hours but have minimal extended-hours participation.
Small-cap stocks (market capitalization under $2 billion) often have extended-hours spreads of $1.00 to $5.00 or wider, and may have no bid or ask quotes available at all in extended hours. These stocks have minimal extended-hours liquidity and should be avoided for extended-hours trading.
For context on how extreme this variation is: an Apple stock ($190 price) might have a $0.10 extended-hours spread (0.05% of stock price). A small-cap stock ($25 price) might have a $2.00 extended-hours spread (8% of stock price). The small-cap stock's spread represents $200 per round-trip trade on 100 shares, while the Apple spread represents only $10 per 100 shares. The execution cost difference is 20-fold.
Spreads and Market Volatility
Spreads widen further during periods of high volatility. When stock prices are moving rapidly and uncertainty is high, market makers increase spreads to protect themselves. Imagine a stock that suddenly moves from $100 to $101 in seconds due to breaking news. A market maker that was providing $0.10 spreads when the stock was stable at $100 will quickly widen spreads to $0.50 or more once volatility spikes. The wider spread compensates them for the higher risk that their bids and asks will become stale as prices continue to move.
Earnings announcements create some of the highest volatility in extended hours, so earnings periods often see the widest spreads. In the first 5 minutes after a company reports earnings at 4:05 PM, spreads can be extremely wide—sometimes $1.00 or more even for large-cap stocks. However, spreads tighten as the initial earnings shock dissipates and traders digest results. By 5:00 PM, spreads have typically narrowed from the initial shock but remain wider than they would be during regular hours.
This volatility-driven spread widening means that traders attempting to execute right when major news breaks (earnings, FDA announcements) face the widest spreads of the entire extended-hours period. Traders who wait 10 to 15 minutes for the initial volatility to subside often find spreads have narrowed and execution costs have declined. This tradeoff—speed of execution versus execution cost—is a key decision point for traders managing earnings or news.
Time-of-Day Effects on Spreads
Beyond the mega-cap versus small-cap categorization, spreads also vary dramatically by time within the extended-hours sessions. In pre-market, spreads are widest very early (4:00 AM to 6:00 AM) when volume is minimal, then gradually narrow as morning approaches. By 9:00 AM to 9:30 AM, pre-market spreads have narrowed considerably from their early-morning levels as more traders enter and volume increases.
In after-hours, the opposite pattern occurs. Spreads are tightest (relatively speaking) in the first 30 to 60 minutes after the close (4:00 PM to 5:00 PM) when volume is highest and market makers have active participation. Spreads then gradually widen as volume declines. By 6:00 PM, spreads have widened substantially from their 4:00 PM levels. By 7:00 PM and later, spreads reach their widest levels.
For traders, the implication is clear: if you must trade in extended hours, do so during the high-liquidity window—early after-hours (4:00 PM to 5:00 PM) or late pre-market (9:00 AM to 9:30 AM)—when spreads are tightest. Avoid very early pre-market (4:00 AM to 6:00 AM) or very late after-hours (after 7:00 PM) when spreads are widest.
Calculating Round-Trip Spread Costs
Understanding the total cost of extended-hours trading requires calculating round-trip spread costs. If you buy and then sell the same position, you pay the spread twice: once when you buy (you pay the ask) and once when you sell (you receive the bid). The total cost is the full spread width times the number of shares.
For example, consider buying and selling 10,000 shares of a mid-cap stock. In regular hours, the spread is $0.02 (bid $99.99, ask $100.01). Round-trip cost is $0.04 per share, or $400 total. In after-hours, the same stock has a spread of $0.50 (bid $99.75, ask $100.25). Round-trip cost is $1.00 per share, or $10,000 total. The extended-hours round-trip cost is 25 times higher.
This calculation demonstrates why extended-hours trading requires profitable price moves to justify the spread costs. If you buy in regular hours at $100 and sell in extended-hours at $100.50, you've made $5,000 on 10,000 shares, but after spreading $500 on the buy and $500 on the sell, your net profit is only $4,000. If the same scenario occurred in extended-hours (buy and sell in extended hours), the spread costs of $10,000 would exceed your $5,000 gross profit, resulting in a $5,000 loss.
Spreads and Price Improvement
Limit orders in extended hours sometimes allow traders to achieve price improvement—execution at a better price than the current bid or ask. For example, if the current bid-ask is $100.00 bid and $100.50 ask, a buyer might place a limit buy order at $100.25. If a seller places a market order or limit sell order at $100.25, the buyer executes at $100.25 instead of the current ask of $100.50, saving $0.25 per share.
Price improvement in extended hours is rarer and smaller than in regular hours. In regular hours, competitive market makers actively provide price improvement by narrowing spreads and accepting limit orders inside the published bid-ask. In extended hours, with fewer market makers, price improvement is less common. Additionally, the wide spreads in extended hours mean that even with price improvement, execution prices remain far worse than regular-hours prices.
Spreads and Different Order Types
Different order types interact differently with spreads in extended hours. Market orders execute immediately at the current ask (when buying) or bid (when selling), incurring the full bid-ask spread as a cost. Market orders guarantee execution (assuming the order book has depth) but at unknown prices.
Limit orders allow traders to specify the price at which they're willing to buy or sell, avoiding the spread cost. A trader can place a buy limit order at the current bid price and potentially execute without paying the spread. However, limit orders risk non-execution if the market moves away from the specified price. In extended hours with wide spreads, limit orders that are placed inside the spread have reasonable odds of execution, while limit orders outside the spread have low odds.
Stop-loss orders and stop-limit orders are prohibited in many extended-hours sessions, as discussed previously. These orders create cascading execution risk when stocks gap significantly.
The Hidden Cost of Spreads
Beyond the direct bid-ask spread cost, there is a hidden cost of wide spreads in extended hours: reduced price discovery and larger overnight gaps. When spreads are very wide in extended hours, fewer traders are willing to transact. This means that fewer transactions occur and prices don't adjust as smoothly to new information. A stock might receive overnight news that should move the stock $2, but with few traders willing to transact due to wide spreads, the stock's price in extended hours might move only $1 before the regular session opens. The next day, the full $2 move occurs at the opening, creating a larger gap.
This gap cost is borne by investors who hold overnight. A position that gaps $2 overnight has lost $2 per share due to overnight holding. While the gap is technically not caused by the spread, it's a consequence of the same low-liquidity environment that produces wide spreads.
Spreads and Market Maker Economics
Understanding spreads requires understanding market maker economics. Market makers profit from spreads. The wider the spread, the more profit they capture per trade. However, market makers also need volume to make profits. A spread of $0.10 on 100 trades per second generates $10 in profit per second. A spread of $1.00 on 2 trades per hour generates $2 in profit per hour. Market makers need enough volume to turn their spread profit into daily profit.
In extended hours, volume is low, so market makers must charge wide spreads to generate sufficient daily profit. The low volume also means that market makers must hold positions longer before they can sell at the ask, increasing their inventory risk. To compensate for longer holding periods, they widen spreads further.
This economic dynamic explains why spreads won't narrow in extended hours unless volume increases substantially. If extended-hours volume were to increase from current levels (2% to 5% of regular volume) to 20% to 30% of regular volume, market makers would have more incentive to participate and would narrow spreads to win order flow. However, traders avoid extended-hours trading partly due to wide spreads and poor execution quality, creating a chicken-and-egg problem: spreads are wide because volume is low, and volume is low partly because spreads are wide.
Real-World Spread Examples
Consider Netflix earnings on January 18, 2024. Netflix reported earnings at 4:05 PM, reporting strong subscriber growth. In the first minute of after-hours trading (4:06 PM), Netflix's spread was $1.20 (bid $437.80, ask $439.00). The stock had been trading with a $0.02 spread ($0.01 bid-ask) during regular hours. In the first 15 minutes of after-hours, volume was high but spreads remained extremely wide at $0.80 to $1.20. By 5:00 PM, as volume declined, spreads tightened somewhat to $0.40 to $0.60. By 6:00 PM, spreads had tightened to $0.20 to $0.30. By 7:00 PM, spreads had narrowed to $0.10 to $0.20, approaching regular-hours levels.
This pattern is typical for stocks reporting earnings: spreads spike immediately after earnings, remain very wide for 30 minutes to an hour, then gradually tighten as volatility declines and volume drops. Traders attempting to exit after earnings at 4:06 PM faced $1.20 spreads. Traders waiting until 6:00 PM faced $0.20 to $0.30 spreads. The time-waiting cost (opportunity cost of holding the position for 2 hours) must be weighed against the execution cost improvement.
FAQ
Q: Why can't spreads narrow further in extended hours?
A: Spreads are limited by the economics of market making. Market makers require sufficient profit margin to compensate for inventory risk and opportunity cost. Lower volume means fewer transactions per spread dollar, forcing spreads to be wider to maintain profitability.
Q: Are extended-hours spreads the same for all brokers?
A: Spreads in extended hours are generally similar across brokers because they're set by the ECNs (electronic communication networks) where trades execute. However, different brokers may route orders to different ECNs, potentially finding slightly different spreads. All spreads are much wider than regular-hours spreads regardless of broker.
Q: Can I negotiate extended-hours spreads?
A: Not for retail investors. Spreads are set by market makers and ECNs. Institutional traders with large order flows sometimes negotiate with market makers for custom terms, but this is not available to individual traders.
Q: How do I avoid paying the full spread?
A: Use limit orders instead of market orders. With a limit order, you might execute inside the spread or at the worst price of your limit. However, limit orders risk non-execution if the market doesn't reach your price.
Q: Why are mega-cap stock spreads so much tighter than small-cap spreads?
A: Mega-cap stocks have higher trading volume and lower overnight gap risk (as a percentage of price), making market maker participation more profitable. Small-cap stocks have low volume and higher gap risk, limiting market maker participation and forcing wider spreads.
Q: Is it better to trade mega-cap stocks in extended hours?
A: Yes, absolutely. Mega-cap stocks like Apple, Microsoft, and Tesla have reasonable extended-hours spreads and liquidity. Small-cap stocks should be avoided for extended-hours trading.
Related Concepts
Bid-ask spreads connect to the broader concepts of market microstructure, transaction costs, and execution quality. The relationship between volume and spreads is fundamental to market economics. Additionally, spreads relate to the concept of market efficiency—in a perfectly efficient market, prices would not move between the bid and ask, but in real markets with imperfect information and inventory risk, the bid-ask spread exists.
The concept of market maker profit is also related. Market makers profit from spreads, and wider spreads represent higher profits per trade but lower profit overall if volume declines. Understanding this tradeoff helps explain why market maker participation varies by stock and time of day.
Summary
Bid-ask spreads in extended-hours trading are 5 to 20 times wider than regular-hours spreads due to lower volume, fewer market makers, and greater inventory risk. Mega-cap stocks have relatively tight extended-hours spreads ($0.05 to $0.15), while mid-cap and small-cap stocks have very wide spreads ($0.50 to $5.00 or more). Round-trip spread costs can easily exceed the profit from short-term trading positions, making extended-hours trading costly for all but the most disciplined traders. Spreads are tightest during high-volume windows (early after-hours, late pre-market) and widest during low-volume windows (very early pre-market, very late after-hours). Using limit orders instead of market orders can reduce spread costs, but avoidance of extended-hours trading during low-liquidity periods remains the most effective cost-reduction strategy for most traders.