Wide bid-ask spreads can silently cost you 1–2% on every trade. We explain how the Slippage Coefficient works and which stocks to avoid.
The price you see on a chart is not the price you actually pay. For liquid, high-volume stocks that gap is trivial — a few basis points at most. For thinly traded names, it can be the difference between a profitable trade and a losing one before the stock has even moved, simply because of what it costs to get in and out.
How the bid-ask spread quietly costs you money
Every trade crosses the spread between the best bid and best ask. On a heavily traded large-cap, that spread might be a single basis point — effectively free. On a low-volume small-cap, it can be 1–2% of the trade value or more, particularly for market orders during quiet hours. That cost is invisible on a standard price chart, but it's very real: you're paying it on the way in, and you'll pay it again on the way out.
The Slippage Coefficient
The Slippage Coefficient estimates, in real time, how much a market order of a given size would move the price against you based on current order book depth. A low coefficient means the stock can absorb your order with minimal price impact. A high coefficient means even a modest order could move the price meaningfully before it's fully filled — a sign that the stock's displayed liquidity is thinner than it looks.
Which stocks to watch out for
The riskiest combination is low average daily volume paired with a wide typical spread — often small-cap names, thinly traded sector plays, or stocks that recently IPO'd and haven't built up consistent trading interest yet. Before sizing into any position in this category, check the Slippage Coefficient on the stock's profile page; if it's flagged high, consider sizing down, using limit orders instead of market orders, or splitting the order across multiple smaller fills to reduce the effective cost of entry.