Spreads and Slippage Explained

The bid-ask spread is the gap between the highest price buyers are offering (the bid) and the lowest price sellers are asking (the ask); slippage is the difference between the price you expected for a trade and the price you actually received. Both are trading costs that do not always show up as a fee, and both grow when liquidity is thin.

For small trades in popular coins on large exchanges, these costs are usually tiny. For larger orders, small tokens or busy market moments, they can be bigger than the trading fee itself. Knowing how they work helps you trade more efficiently and avoid nasty surprises.

What the Bid-Ask Spread Is

An exchange's order book lists buy orders (bids) and sell orders (asks). The best bid is the highest price someone will pay right now; the best ask is the lowest price someone will sell for.

Example:

If you buy with a market order and immediately sell with a market order, you lose the spread — about 0.2% here — before any fees. That is why the spread is called an implicit cost.

What makes spreads wide or tight

• Liquidity. Popular pairs with many active market makers have tight spreads.
• Volatility. In fast markets, market makers widen spreads to protect themselves.
• Exchange size. Smaller venues often have wider spreads.
• Time of day. Liquidity can be thinner during quieter hours.

Read what is liquidity and why it matters for the bigger picture.

What Slippage Is

Slippage is the gap between the price you expected and your average fill price. It has two main causes:

1. 1Market movement. The price changes between when you click and when your order executes.
2. 2Order size versus depth. A large market order consumes the best-priced orders, then moves on to worse prices.

Example on an order book:

A market order to buy 10 units fills 2 at $100.10, 3 at $100.30 and 5 at $100.80. The average price is about $100.51 — roughly 0.4% worse than the $100.10 you saw at the top of the book. That difference is slippage.

Slippage on Decentralized Exchanges

On automated market maker DEXs, there is often no order book. Prices come from a formula based on the pool's reserves, so every trade moves the price. This is called price impact: the bigger your trade relative to the pool, the worse your price. See automated market makers explained.

DEXs let you set a slippage tolerance, such as 0.5% or 1%. If the final price would be worse than that, the swap fails.

• Too low: swaps fail often, especially for volatile tokens, and you pay gas for failed transactions on some networks.
• Too high: bots can exploit you through front-running and sandwich attacks, buying before you and selling after you to capture the gap.

Some scam tokens also require very high slippage because they charge hidden taxes on transfers. If a token only works with 10% or higher slippage, investigate before trading.

How to Reduce Spread and Slippage Costs

1. 1Use limit orders on centralized exchanges to set the exact price you accept. You may not get filled, but you avoid paying the spread.
2. 2Trade liquid pairs on reputable venues, where spreads are tight and order books deep.
3. 3Split large orders into smaller pieces over time.
4. 4Check order book depth or price impact before trading.
5. 5Avoid trading during extreme volatility, such as right after major news.
6. 6Use DEX aggregators that route across several pools to reduce price impact. See DEX aggregators.
7. 7Set a sensible slippage tolerance and raise it only when you understand why it is needed.

Our step-by-step guide on how to avoid slippage on DEX trades covers DEX settings in more detail.

How These Costs Add Up

For a long-term investor buying a large, liquid coin occasionally, spreads and slippage are minor. For frequent traders or anyone trading small tokens, they can be the largest cost. A simple way to see your total cost is to compare your average fill price with the mid-price at the moment you traded, then add fees.

Consider an illustrative round trip in a thinly traded token: a 1% spread, 1% slippage on the way in, 1% slippage on the way out and 0.2% in fees each way. Before the price moves at all, you are down more than 3%. In a liquid major pair, the same round trip might cost a small fraction of that. The token has to rise by more than your total trading costs just for you to break even.

Spreads and Slippage as Warning Signs

These costs are also useful research signals. A token with a persistently wide spread, a very shallow order book or a DEX pool where small trades cause large price impact has limited real liquidity. That can mean:

• You may struggle to sell when you want to, especially in a market drop.
• The quoted price may not reflect what you could actually sell for.
• Reported trading volume may be inflated. See how to evaluate trading volume quality on exchanges.

Checking depth before you buy is a quick way to avoid getting stuck in a position you cannot exit.

Bottom line

The bid-ask spread is the cost of trading immediately, and slippage is the extra cost of market movement and limited liquidity. Both rise in thin, volatile markets and with large orders. Use limit orders, liquid pairs, sensible slippage settings and smaller order sizes, and always check the price impact before you confirm a trade.