Does high volume mean you can always sell?
Crypto ranking sites show daily trading volumes in the billions. High volume suggests you can trade whenever you like at a fair price, but how much a specific order will cost you depends on the orders resting in the book right now, not on yesterday's volume.
This guide explains the difference between volume and liquidity, how to read spreads and market depth, and how slippage grows with order size, using a hypothetical order book. It also covers differences between exchanges, what happens to liquidity in a crash, and what to check before placing a large order.
Volume is not liquidity
Volume is the total value traded over a period. Liquidity is how much you can trade right now without moving the price much. A coin can show large daily volume concentrated in a few minutes of frantic trading, or generated by a handful of accounts, and still have few willing counterparties at this moment.
Some exchanges have also been criticized for wash trading, where the same party buys and sells to inflate volume. Looking directly at the spread and depth of the order book is a more reliable guide than the volume figure.
Spread and depth
The spread is the gap between the highest price a buyer is offering (the bid) and the lowest price a seller will accept (the ask). The wider the spread, the more you lose by buying and immediately selling, and the further the actual fill can be from the displayed "last price."
Depth describes how many orders sit at prices beyond the best bid and ask. The SEC's Investor.gov explains that a market order guarantees execution but not price. In a shallow market, a large market order works through several price levels, and the average fill gets progressively worse.
Working out slippage by order size
Suppose a hypothetical exchange shows a best bid of 99.5 and asks of 2 units at 100.0, 3 units at 100.5, and 5 units at 101.0. As the size of a market buy increases, the average price rises like this:
| Units bought | Fills | Average price | Vs. best ask |
|---|---|---|---|
| 2 | 2 at 100.0 | 100.00 | +0.00% |
| 5 | 2 at 100.0 + 3 at 100.5 | 100.30 | +0.30% |
| 8 | Above 5 + 3 at 101.0 | 100.56 | +0.56% |
| 10 | Above 5 + 5 at 101.0 | 100.65 | +0.65% |
Measured from the mid-price of 99.75, buying 10 units costs about 0.9% more. The thinner the book, the bigger this gap for the same size.
Liquidity differs by venue
The same coin can have different prices, depth, and deposit or withdrawal availability on each exchange. A ranking site's total volume aggregates many venues and says little about the one you use. Fiat pairs, stablecoin pairs, and futures are also separate markets.
On decentralized exchanges, a liquidity pool sets the price instead of an order book. Uniswap's documentation explains that price impact grows as a trade gets larger relative to the pool, and that slippage, price movement between submitting and executing a trade, must be considered separately. Setting a very wide slippage tolerance can lead to a poor fill.
Liquidity that disappears in a crash
An order book that looks deep on a calm day can thin out in seconds during a sell-off or an outage. Market makers pull orders to limit risk, and if an exchange pauses deposits or withdrawals, prices across venues can drift apart. The CFTC warns that virtual currency prices are highly volatile and that trading platforms can fail or halt.
The assumption that you can always sell tends to be weakest exactly when you most want to sell. For larger holdings, it is worth checking how spreads and depth behaved during past periods of stress, not just today.
Before placing a large order
These checks can be done on the exchange you actually use, just before trading.
- Note the best bid and ask and express the spread as a percentage of the mid-price.
- Apply your order size to the visible book and calculate the average fill and its gap from the best price.
- If the gap is large, consider a limit order or splitting the order into smaller pieces.
- On a DEX, check the displayed price impact and keep slippage tolerance no wider than necessary.
- Check the exchange's deposit and withdrawal status, its outage history, and its price gap to other venues.
The limits of liquidity measures
An order book is a snapshot, and visible orders can be cancelled just before you trade. Some liquidity, such as hidden orders or routing to other venues, does not appear on screen, so actual slippage can differ from your estimate.
The order book and calculations above are hypothetical. In real trading, check the book and the exchange's status right before you act, and remember that liquidity varies widely by time of day and market conditions.