BitMEX uses three price types. Last price is the most recent trade price on BitMEX. Index price is the weighted average price from multiple external exchanges. Mark price is derived from the index price using the funding basis and is used to calculate position margin, unrealised PNL, and trigger liquidations. Mark price prevents price manipulation from affecting margin calculations.
What Is Last Price on BitMEX?
Last price is the most recently traded price on the BitMEX exchange. It reflects the price at which contracts were last bought and sold.
Last price can deviate from the underlying index price due to market dynamics on the BitMEX order book. Short-term supply and demand imbalances on the platform can push the last traded price above or below the broader market price.
Last price is relevant for trade execution and as a trigger option for stop and take profit orders.
What Is Index Price on BitMEX?
Index price is the weighted average price of the underlying asset, calculated from prices across multiple exchanges. For XBTUSD, the index is .BXBT.
The index provides a reference price that represents the broader market rather than the conditions on any single exchange. Using multiple exchanges makes the index resistant to manipulation or temporary price spikes on individual platforms.
The full list of indices, their component exchanges, and weightings is available on the BitMEX Indices page.
What Is Mark Price on BitMEX?
Mark price is a derivation of the index price used to prevent price manipulation from affecting critical calculations. BitMEX uses mark price for three purposes:
- Position margin calculation: Determines how much margin a position requires.
- Unrealised PNL calculation: Shows your current profit or loss on open positions.
- Liquidation triggers: Determines when a position is liquidated.
The mark price equals the index price multiplied by the funding basis. The funding basis is calculated as: Funding Rate x (Time Until Funding / Funding Period). Full details on the exact calculation are available on the Fair Price Marking page.
Using mark price rather than last price protects traders from liquidation caused by temporary price wicks or manipulation on the BitMEX order book.