What Is Bid-Ask Spread? How It Affects Every Trade You Make

What Is the Bid-Ask Spread?

Every stock has two prices displayed simultaneously:

• Bid price: The highest price a buyer is currently willing to pay for the stock
• Ask price (also called the "offer"): The lowest price a seller is currently willing to accept

The difference between these two prices is the bid-ask spread. When you look at a stock and see "Bid: $50.05 / Ask: $50.10," the spread is $0.05 (5 cents).

The spread represents the cost of immediacy. If you want to buy a stock right now using a market order, you pay the ask price. If you want to sell right now, you receive the bid price. The spread is the transaction cost paid to market makers — the firms that continuously quote buy and sell prices to maintain liquidity.

Algorithmic market making has transformed spreads: With algorithmic trading driving 60-70% of U.S. equity volume, automated market makers now dominate quote provision. This has compressed spreads on liquid large-cap stocks to fractions of a penny during normal conditions — but it has also made spreads more volatile during news events, as algorithms withdraw liquidity faster than human market makers ever did. Understanding this dynamic is critical for any active trader.

Why the Bid-Ask Spread Matters

The bid-ask spread is often called a "hidden" cost because it does not appear on your brokerage commission statement. But it is a real and significant cost, especially for frequent traders.

Example: Stock XYZ has a bid of $25.00 and an ask of $25.05. You buy 100 shares at the ask ($25.05) and immediately decide to sell at the bid ($25.00). Without any price movement, you have lost $5 — the spread — on the round trip.

For day traders executing dozens of trades per day, the spread can easily exceed commissions in total cost. A trader making 20 round trips per day on stocks with a $0.05 spread spends $100 per day in spread costs alone (on 100-share lots).

Factors That Determine Spread Size

Liquidity: Highly liquid stocks (high daily volume, many buyers and sellers) have tight spreads. Apple (AAPL), which trades hundreds of millions of shares per day, typically has a $0.01 spread. A thinly traded micro-cap might have a $0.20–$0.50 spread.

Market hours: Spreads widen significantly in pre-market and after-hours trading when fewer participants are active. A stock with a $0.01 spread during market hours might have a $0.10 spread at 8 AM. See the full pre-market trading guide for details on extended hours risks.

Volatility: During fast-moving markets (major news events, earnings reactions, market open), market makers widen spreads to compensate for increased risk. High-volatility stocks carry wider spreads.

Price level: Penny stocks with low absolute prices can have spreads that represent 2–5% of the stock's value — an enormous transaction cost. A stock priced at $0.50 with a $0.02 spread has a 4% spread.

Time of day: The market open (9:30–10:00 AM ET) and market close (3:30–4:00 PM ET) have the tightest spreads due to peak participation. Midday (11:30 AM–1:30 PM) often sees wider spreads as liquidity thins.

How to Minimize Bid-Ask Spread Costs

1. Trade liquid stocks Focus on stocks with daily volume above 1 million shares and a spread of $0.01–$0.05. The major S&P 500 components, popular ETFs (SPY, QQQ, IWM), and high-volume tech stocks all offer tight spreads. Avoid low-float, low-volume stocks unless the setup is exceptional — their wider spreads require larger moves just to break even.

2. Use limit orders Market orders fill at the ask when buying and at the bid when selling — you always pay the full spread. Limit orders allow you to specify the price you're willing to pay or accept. Buying at the midpoint of the spread (between bid and ask) can capture partial spread savings, though your order may not always fill immediately. See market order vs. limit order for a full comparison.

3. Trade during peak hours Spreads are tightest during the first and last hours of regular trading (9:30–10:30 AM and 3:00–4:00 PM ET). If you trade pre-market or after-hours, factor in the significantly wider spreads in your risk/reward calculation.

4. Consider the spread in your profit target Before entering a trade, calculate whether your target return justifies the spread cost. If a stock has a $0.15 spread and your profit target is $0.20, you are risking significant capital for marginal edge. Generally, your target should be at minimum 3–4x the spread to make the trade worthwhile.

5. Check Level 2 quotes Level 2 market data shows the full order book — all bids and asks at different price levels. This reveals whether the spread is temporarily wide (few orders at the inside bid/ask) or structurally wide (thin throughout the book). A temporarily wide spread might offer an opportunity to get filled between bid and ask.

Bid-Ask Spread vs. Commission

Many brokers now offer commission-free trading, leading some traders to believe stock trading is free. It is not — the spread is the primary remaining cost. Market makers pay brokers for order flow (a practice called payment for order flow, or PFOF) and make their profit from the spread.

A broker charging $0 commission but routing orders to a market maker who executes at a $0.03 spread might cost you more than a broker charging $1 per trade with better execution at a $0.01 spread. Execution quality — how close to the midpoint of the bid-ask spread your orders fill — matters more than the headline commission rate for active traders.

How the Bid-Ask Spread Affects Different Order Types

Understanding how spread interacts with different order types is essential for optimizing execution:

Market orders: Always pay the full spread. A market buy executes at the ask; a market sell executes at the bid. The spread is an immediate, certain cost. Market orders are appropriate when speed matters more than price precision — urgent exits, stop-loss triggers, or fast-moving momentum entries.

Limit orders: Allow you to post your bid or ask inside the current spread, potentially capturing part or all of it. A limit buy placed at the midpoint of a $0.05 spread might save $0.025 per share. However, limit orders carry non-execution risk — if the price moves away from your limit, you miss the trade entirely.

Stop-limit orders: Trigger at the stop price and then attempt to fill at the limit price or better. If the stock gaps through your limit price (common on volatility spikes), the order may not execute at all, leaving you with an unhedged position.

For most day traders, the optimal approach is limit orders for entries (prioritize price) and aggressive limit orders that track the ask for exits (prioritize execution with minimal slippage beyond the spread).

Spread Costs Across Asset Classes

The bid-ask spread varies enormously across different markets:

The pattern is consistent: the more liquid and widely-traded an instrument, the tighter the spread. This is why professional traders focus on the most liquid names — the spread cost advantage compounds across hundreds of trades per year.

How Market Makers Set the Spread

Market makers continuously adjust their quoted spreads based on several real-time factors:

Inventory risk: If a market maker has accumulated a large long position in a stock, they widen the ask (make buying more expensive) to discourage further buying and reduce their inventory. If they're short, they widen the bid.

Volatility: Higher implied volatility means the stock can move more against the market maker's inventory between quotes. They widen spreads to compensate for this increased adverse selection risk.

Time of day: At the open and close, when institutional order flow is heaviest and directional, market makers widen spreads. In the quiet midday period, spreads narrow because the risk of being on the wrong side of informed order flow is lower.

News events: Around earnings, FDA announcements, and major macro data releases, market makers widen spreads dramatically — sometimes 5–10x normal — to avoid being picked off by traders with advance knowledge or superior analysis.

Understanding these dynamics helps you time your entries. Entering a trade 5 minutes after a news event, once the initial spread widening has resolved, often results in meaningfully better fills than entering the moment headlines cross.

How Tradewink Accounts for Bid-Ask Spread

Tradewink's position sizing and screener algorithms incorporate estimated spread costs into trade evaluation. The cost modeling system estimates round-trip spread costs based on historical spread data for each stock and factors this into the expected value calculation for each trade signal.

Stocks with spreads wider than a configurable threshold are filtered out of the screener by default. This prevents signals on thinly-traded stocks where the spread alone would consume a significant portion of the expected profit. When you receive a Tradewink signal, bid-ask spread cost is one of the factors already absorbed into the risk/reward analysis.