How to read a crypto order book

The book is not a prediction device. It is a live map of what your order will cost and where other people have decided price matters — and it is honest about the first and unreliable about the second.

Last verified 13 September 2026 · written by the DexLadder team

The anatomy

Bids are resting buy orders below the current price; asks are resting sells above it. The best bid and best ask define the spread, and the midpoint between them is what charts usually draw. Everything beyond the top of the book is depth: the size waiting at each successive price level.

What it tells you reliably

Your cost. A market order walks the book, consuming each level in turn. Add up the size until it covers your order and you have your true average fill — not the number on the ticker.
Whether this market fits your size. Sum the resting size within 0.5% of mid. If your intended order is a meaningful fraction of it, you are the market event.
Where liquidity thins. Gaps in the ladder are where price travels fastest, because there is nothing to slow it down.

What it tells you unreliably

Large resting orders are the most over-interpreted object in trading. They can be cancelled in a millisecond, and frequently exist to be seen rather than filled — placed to create the impression of support, then pulled the moment price approaches. Treat a visible wall as information about intent to influence, not about actual demand. Iceberg orders do the reverse: real size hidden behind a small visible slice, so genuine depth can be invisible.

A worked example

Side	Price	Size
Ask	68,430	9 BTC
Ask	68,420	4 BTC
Ask	68,415	2 BTC
Bid	68,410	4 BTC
Bid	68,405	11 BTC

A market buy for 6 BTC takes 2 at 68,415 and 4 at 68,420 — an average of 68,418.33, not the 68,415 you saw quoted. Buying 12 BTC instead reaches into 68,430 and the average drifts further. The spread is 5 points; crossing it twice on a round trip costs roughly 0.015% before fees, which is trivial here and very much not trivial on a thin altcoin.

The habit worth building

Before every market order, ask one question: how much of the visible depth within half a percent does this order consume? Under a tenth, trade it. Approaching a third, use a limit order or split it. Over half, you are not trading this market — you are moving it, and something like a TWAP is the right tool.

Calculators for this

Price impact calculator

Terms used here

Order book Bid-ask spread Market depth Limit order Slippage

Questions people actually ask

What is depth in an order book?

The total size resting at prices near the current one. It determines how much you can trade before your own order moves the price.

Are big orders in the book real?

Often not. Resting orders can be cancelled instantly, and size is frequently displayed to influence behaviour rather than to be filled.

Does an order book exist on a DEX?

Most decentralised venues use an AMM pool instead, where price comes from reserves rather than resting orders. Some chains do host real on-chain books.

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