BitMEX uses the Mark Price, not the Last Price shown on the chart, to trigger liquidations. The Mark Price is derived from the spot index price and can differ from the chart price. If the Mark Price reached your liquidation price, the liquidation was triggered correctly, even if the chart price did not appear to reach that level.
Why does the chart price differ from the liquidation trigger price?
The price displayed on the BitMEX trading chart is the Last Price – the most recent price at which a trade was executed on the BitMEX order book. This is not the price BitMEX uses to trigger liquidations.
BitMEX uses the Mark Price for all liquidation calculations. Mark Price is a fair-value estimate derived from the underlying spot index price, adjusted for the funding basis. It is designed to prevent liquidations caused by market manipulation or temporary price dislocations on a single exchange.
The Last Price and the Mark Price can diverge, especially during:
- Low-liquidity periods. When the order book is thin, the Last Price can spike or dip without the Mark Price following.
- High volatility. Rapid price movement can create temporary gaps between the two prices.
- Funding basis shifts. Changes in the premium or discount of the perpetual price relative to spot can move the Mark Price independently.
How can I check the Mark Price?
The Mark Price is displayed in the contract details section of the BitMEX trading interface. It appears alongside the Last Traded Price and the Index Price.
You can also view historical Mark Price data through the BitMEX API. The markPrice field on trade records shows the Mark Price at each point in time.
Always monitor the Mark Price, not just the chart price, when managing positions close to their liquidation level.
How can I protect against Mark Price divergence?
Three measures reduce the risk of unexpected liquidation from Mark Price divergence:
- Reduce leverage. Lower leverage increases the gap between the current price and your liquidation price. A larger buffer absorbs minor divergences between Mark Price and Last Traded Price.
- Set wider stop-losses. Place stop-loss orders with enough margin to account for the potential difference between the chart price and the Mark Price.
- Monitor the Mark Price directly. Keep the Mark Price visible on your trading interface. Do not rely solely on the chart candles, which reflect the Last Traded Price.