Volume measures turnover, not a price guarantee
A venue can report substantial daily turnover while displaying little quantity near the current price. The same inventory can trade repeatedly during a day, and the book can change after those trades. Dividing your order value by reported daily volume therefore does not calculate the price impact of executing immediately.
Binance provides separate endpoints for historical trades, 24-hour ticker statistics and depth. This separation is useful in analysis: a volume measure needs a time window, while a depth measure needs a snapshot and a price range. Label both, including whether quantity is expressed in BTC or the quote currency.
Calculate a purchase across several ask levels
Take an illustrative ask book with 0.05 BTC offered at 60,000 USDT, another 0.10 BTC at 60,030 and another 0.20 BTC at 60,100. A 0.20 BTC market purchase would consume all of the first two levels and 0.05 BTC from the third, assuming those offers remain available.
The estimated cost is 3,000 plus 6,003 plus 3,005, totaling 12,008 USDT. Dividing by 0.20 BTC gives an average fill of 60,040 USDT. Against the best ask of 60,000, the estimated slippage is 40 USDT per BTC, or approximately 6.67 basis points. The order pays 8 USDT more than an unrealistically unlimited fill at the best ask. Trading fees are additional.
Use a reference price that matches the question
Slippage relative to the best ask isolates the extra cost of consuming deeper asks in this static example. Slippage relative to the midpoint also includes crossing half the quoted spread. Comparing one venue's midpoint-based estimate with another venue's best-ask-based estimate creates an inconsistent ranking.
For a sell order, walk bids from highest price downward. For a fixed spending budget, convert each consumed quote amount into base quantity as you move through asks. An aggregated book already combines quantity at each price; Coinbase's documentation explicitly warns that the displayed aggregate size should not be multiplied by the number of underlying orders.
Treat a depth estimate as a conditional calculation
The worked example assumes unchanged liquidity during execution. Actual orders may arrive, cancel or fill while a request travels to the venue. A shallow snapshot can also omit prices needed for a larger order. Show insufficient visible depth when necessary, and record the snapshot timestamp rather than presenting an estimated fill as certain.
For venue comparisons, use the same asset, quote currency, order size, fee assumptions and slippage reference. Calculate several sizes to reveal where a venue's apparent advantage disappears. A book with the lowest initial ask can still be more expensive for your full quantity. Depth is valuable precisely because it lets you replace a single headline price with a size-specific estimate.
Questions about this tool
Does a visible buy wall guarantee support?
No. It is displayed interest at one moment. Those orders can change before a sell order reaches them, so the wall is not a guaranteed future execution price.
Can I estimate slippage from just the best bid and ask?
Only for a quantity fully covered by the displayed size at that level, and still subject to change. Larger orders require deeper price-and-quantity data.