The definition
A spread is the difference between two prices. Which two depends on the context, and the confusion here costs people money.
The spread inside one market
An order book always carries two prices: the bid, what buyers offer right now, and the ask, what sellers want. The ask is always above the bid, and the gap between them is the book spread. Buy at the ask and sell instantly at the bid and you are down by exactly that amount — it is the cost of entering the market.
On BTC/USDT at Binance that spread is hundredths of a percent. On an illiquid coin it can be 2–3%, and the purchase alone is already a loss to work off.
The spread between exchanges
The same coin costs slightly different amounts across venues: more buyers here, closed withdrawals there, a market maker gone somewhere else. The gap between the best buy price on one exchange and the best sell price on another is the cross-exchange spread, which is what the CEX arbitrage page looks at.
The spread between different market types
Spot and futures on one coin are separate markets with separate participants, and their prices drift apart. That difference is the basis, and the funding rate is the fee for holding it. The gap between a DEX pool price and an exchange price belongs to this family too.
The spread on P2P
P2P spreads are unusually wide because the price is set by a person, not an algorithm: the merchant prices in their margin, the risk of a frozen card and the time spent on the chat. A 3–5% gap between the best buy and the best sell is normal there, not an anomaly.
Why the net figure is always smaller
The visible spread is a price before deductions. Four things stand between it and money in your account:
- Trading fees. Always two of them: buy and sell. On spot that is typically 0.1% + 0.1%.
- Transfer costs. A withdrawal fee or network gas. Independent of size, so it kills small trades.
- Depth. The best price is available for a small amount. Beyond it you walk up the book and your average fill is worse than the top line.
- Time. Prices move while funds travel between venues. On a volatile coin ten minutes can erase or reverse the spread.
That is why every table on this site carries a separate Net column — and why you should always sort by it rather than by the raw spread.
One rule worth keeping
A large spread is almost never a gift. A 20–50% gap between venues means, nine times out of ten, one of three things: the ticker is a different coin, withdrawals are closed, or there is no money in the book. Real arbitrage spreads are modest — fractions of a percent and low single digits. That is exactly why they are so crowded.