Read price and quantity as separate inputs
Each ask level contains a selling price and the base-asset quantity offered at that price. For a BTC/USD book, quantity is BTC and price is USD per BTC. The modeled market buy consumes asks from the lowest price upward. Enter the rows in ascending price order.
This calculator uses the ask side only. Mixing bids and asks creates an execution path that is not available. Enter the size shown at each level rather than a cumulative quantity, unless you first convert cumulative values back into individual levels. A market sell requires a separate bid-side calculation.
How average price and slippage are calculated
The model fills as much as possible at the best level, then uses the next level until the requested quantity is filled or the supplied book is exhausted. Total quote value is the sum of each filled quantity multiplied by its price. Average execution price is that total divided by the filled base quantity.
Buy slippage is the average execution price above the best ask, expressed as a percentage of that best ask. This is book-walking slippage against the snapshot's best buying price; it does not measure movement between the moment you decide to trade and the moment the order executes.
What an incomplete fill tells you
If the entered ask levels do not contain enough size, the calculator reports insufficient depth instead of inventing a full-order average. The remaining quantity is unknown rather than free liquidity at the last supplied price. Obtain deeper data or reduce the modeled quantity before calculating again.
Trading fees are separate from the depth calculation. Cancellations, hidden liquidity, exchange order protections and other traders can change the actual outcome. Use the resulting average price in a broader trade-cost or arbitrage calculation, with the snapshot's age and limitations in mind.
Questions about this tool
Should I paste individual level sizes or cumulative order-book totals?
Use the quantity available at each individual price. If your exchange displays cumulative depth, subtract the previous cumulative total from the next one before entering the levels.
Why is actual slippage different from this result?
The model assumes the entered book remains unchanged while the order fills. Real orders can be added, canceled or consumed between the snapshot and execution, and exchange protections may limit the submitted order.