Why you should care about the spread
When you buy a stock, you pay the ask price. When you sell, you receive the bid price. The difference between those two prices is the spread. It is the fee you pay to the market maker or the exchange, and it is invisible if you only look at your brokerage statement. For active traders, the spread can eat a meaningful portion of returns. For occasional investors, it matters less, but it still affects the price you get.
Most retail investors focus on commissions and fees. Those are explicit and easy to compare. The spread is implicit and varies by stock, by time of day, and by market conditions. Ignoring it is like ignoring the tax on a transaction.
What determines the spread?
Liquidity is the core driver. A stock is liquid when there are many buyers and sellers willing to transact at close prices. High liquidity means tight spreads, often just a few cents. Low liquidity means wide spreads, sometimes several percent of the stock price.
Take a large-cap index ETF like SPY. Millions of shares trade daily, and the spread is usually one cent. Now consider a small-cap stock with a market cap under $100 million. It might trade a few thousand shares a day, and the spread could be 10 or 20 cents. On a $5 stock, that is a 2% to 4% round-trip cost. You need the stock to move that much just to break even.
Why does liquidity vary? It comes down to the number of market participants and the risk they are willing to bear. Market makers quote bid and ask prices to earn the spread, but they take on inventory risk. If they buy from a seller and cannot find a buyer, they are stuck with a position that could lose value. For illiquid stocks, that risk is higher, so they widen the spread to compensate.
Another factor is volatility. When a stock is volatile, the price can move between the time a market maker quotes a price and the time the order executes. To protect against that, they widen the spread. So a stock that is both illiquid and volatile will have a very wide spread. That combination is common in small biotech or mining companies with binary news events.
How the spread affects your trades
The spread is not just a cost on entry; it is also a cost on exit. If you buy a stock at the ask and immediately sell at the bid, you lose the full spread. That is a guaranteed loss, regardless of the direction of the stock. For a day trader who makes many round trips, the spread can be larger than the commission.
Consider a stock priced at $50 with a bid of $49.95 and an ask of $50.05. The spread is $0.10, which is 0.2% of the price. If you buy and sell within the same day, you need the stock to rise at least $0.10 just to break even. That is a hurdle that many trades cannot clear.
But the spread also affects market orders. If you place a market order to buy, you will almost always get the ask or worse. If you place a limit order to buy at the bid, you might wait a long time, or the order might not fill at all. The spread is the price of immediacy. You pay more when you need execution now.
Practical tips to reduce spread costs
First, use limit orders. A market order guarantees execution but not price. A limit order guarantees price but not execution. For liquid stocks, a limit order at the midpoint (between bid and ask) often fills within seconds. For illiquid stocks, you may need to adjust your limit to the ask to get a fill, but at least you know what you are paying.
Second, trade during liquid hours. The first and last 15 minutes of the trading day often have wider spreads because of uncertainty and low participation. The middle of the session, especially between 10 a.m. and 3 p.m. Eastern, usually has the tightest spreads. If you can, avoid trading at the open and close.
Third, avoid illiquid stocks unless you have a strong reason. If you are a long-term investor, a wide spread is a one-time cost that you can amortize over years of holding. But if you are a trader, that cost repeats every time you enter and exit. For short-term strategies, the spread can be the difference between a profitable edge and a losing one.
Fourth, check the spread before you trade. Most brokerage platforms show the bid and ask. If the spread is more than 0.5% of the stock price, ask yourself if the trade is worth it. Sometimes it is, but you should make that decision consciously.
ETFs are not immune to spread issues. While large ETFs like SPY or QQQ are very liquid, sector or thematic ETFs can be surprisingly illiquid. A small ETF tracking a niche index might have a wide spread, even if the underlying stocks are liquid. That happens because the ETF itself trades less frequently than its components. The market maker has to hedge with the underlying stocks, and if the ETF is small, the quoting risk is higher.
Indices themselves have no spread, but if you trade futures or options on an index, the spread applies to those instruments. Index futures like the S&P 500 futures are highly liquid, but options spreads can be wide, especially for out-of-the-money strikes. Options traders often overlook the spread because they focus on the premium, but the spread is part of the cost of each contract.
When the spread is not the main problem
There is a nuance. For long-term investors who buy and hold for years, the spread is a minor cost. A 0.2% spread on a position held for five years is negligible compared to the expected return. The real cost is the opportunity cost of not investing, or the risk of picking the wrong stock. So the spread matters most for active traders and for those who trade small, illiquid names.
Another nuance: the spread is not a fixed cost. It changes with market conditions. During a market crash, spreads widen dramatically because volatility spikes and market makers pull back. If you need to sell during a panic, you will pay a wider spread. That is a risk to plan for, not a reason to avoid trading.
What to do next
Start by measuring the spread on the stocks you trade. For your next few trades, write down the bid and ask before you place an order. See how often your limit order fills and at what price. Over a week, you will have a sense of the hidden cost you have been paying.
Then, adjust your strategy. If you are a day trader, consider switching to more liquid names. If you are a swing trader, avoid entering during the first and last minutes of the session. If you are a long-term investor, use limit orders at the midpoint and be patient.
The spread is not a mystery. It is a market mechanism that reflects risk and liquidity. Once you understand it, you can make better execution decisions. That is not financial advice; it is just the mechanics of trading. The rest is up to you.
This article is for educational purposes only and does not constitute investment advice.