Mark Price vs Index Price vs Last Price: Why Your Liquidation Triggers There

The Mark Price Is Fair Value, Derived From the Index

The mark price is the one that actually values your position. It starts from the index price and then applies a small fair-value adjustment so the contract is marked at what it is genuinely worth right now, not at whatever the last trade happened to print.

Why adjust at all? Because a perpetual or a dated future does not always trade exactly at spot. It carries a basis: it can sit slightly rich or slightly cheap to the index depending on whether longs or shorts are paying, and that lean is shaped by funding. Mark price formulas fold in a short, smoothed read of that basis. Deribit, for example, computes mark price as its index plus a short exponential moving average of the deviation between its fair price and its index. Bybit takes a median of three inputs: the index adjusted by a funding-basis term, the index plus a moving average of the order book's deviation from the index, and the last traded price. Different venues, different recipes, but the shape is the same: index price as the anchor, plus a brief memory of how the contract has been quoted relative to spot.

The crucial detail in those formulas is the moving average. Mark price does not react to a single trade. It uses a smoothed window, often measured over seconds, of how the contract's mid-market quote has been sitting against the index. A lone wick has almost no weight in an average that samples every second across a half-minute or more, which is precisely the point.

Why Liquidations Trigger Off Mark Price

Now the candle that did not touch your level makes sense. Exchanges value unrealized PnL and trigger liquidations off mark price, not last price. Binance states this directly: it uses mark price as the liquidation reference specifically to avoid unnecessary liquidations during volatility and to discourage manipulation. Deribit uses mark price for unrealized PnL, margin calculations, and liquidation checks alike.

If venues liquidated off last price, every shallow wick would become a liquidation event. One trader with enough size to spike a thin book for a single second could trigger a cascade of forced closes and buy back the unwound positions cheaply. Anchoring liquidations to a smoothed, multi-venue-derived mark price removes that attack surface. Your position is judged against fair value, not against the worst tick anyone managed to print on your exchange.

So the candle on your screen can show a low that never reached your liquidation level, yet your position still closes, because at that instant the mark price reached it even though the last price did not. It also runs the other way: a violent last-price wick can leave your position untouched because mark price never confirmed the move. One more practical note: exact mark-price formulas vary by exchange, so the same position with the same leverage can liquidate at slightly different moments on different venues. Always check which price your exchange marks against before you size a position.

Read All Three, Not Just the Candles

Last price tells you where the most recent trade happened on one venue. Index price tells you where the broader spot market actually is. Mark price tells you what your position is worth and where it lives or dies. Trade the chart on last price if you like, but manage your risk on mark price, because that is the number the exchange is watching.

Athenum aggregates order flow, open interest, funding, liquidations and options across 14 exchanges, sub-second, so you can see how price, basis and funding are lining up across venues instead of staring at one candle. The free tier is currently delayed and limited, but the 7-day Pro+ trial is the full real-time read across all 14 exchanges with no card required. Start free at app.athenum.xyz/auth.