Mark Price vs Last Traded Price in Perpetual Futures Explained

02 September 2026

You open a perpetual futures position. You watch the orderbook. The last traded price moves against you, but not by much. You feel safe. Then your position is liquidated. What happened?

The mark price happened.

Mark price is a synthetic price, not the price at which anyone last traded on your exchange. It is derived from a spot index plus a decaying basis. The spot index averages prices from multiple spot exchanges. The basis is the premium or discount between the perpetual's price and that index, decayed over time. The goal is simple: prevent manipulation wicks on a single exchange from triggering liquidations.

A whale can dump on one exchange. The last traded price on that orderbook can plunge. But the mark price barely moves. Your liquidation is based on the mark price. Not the orderbook you were watching.

Different exchanges calculate mark price differently. The differences matter.

Binance uses a two-component system. First, it takes a spot index from a basket of major spot exchanges. Second, it adds a "fair price adjustment" based on the funding rate. The adjustment decays the basis over the funding interval, and Binance's mark price is recalculated every few seconds. It smooths out sudden orderbook spikes. A trader watching only Binance's last traded price might see a flash crash to $10,000; the mark price might only move to $10,050. The liquidation threshold, set against mark price, stays far away.

Bybit uses a similar logic but with different weights. Bybit's mark price is the median of three values: the spot index, the last traded price, and the "fair price" (which is the moving average of the last traded price minus the basis). The median removes outliers. If a single exchange wicks, the last traded price becomes an outlier, and the median ignores it. Bybit also adjusts the basis decay more aggressively than Binance. Their mark price tends to converge to the index faster after a funding rate change.

dYdX operates differently because it is an on-chain orderbook. Its mark price is the time-weighted average of the spot index over the last 30 seconds, plus a drift adjustment. There is no central exchange to set the last traded price. The last traded price on dYdX's orderbook can deviate significantly from the index if liquidity is thin. But the mark price does not follow. dYdX's liquidation engine uses this synthetic mark price exclusively. A trader on dYdX who only watches the orderbook sees a price that might not match the liquidation trigger at all.

Why does this blindside traders? Because the last traded price is what you see on the chart by default. It is what the orderbook shows. It is visceral. The mark price is a background calculation, and most interfaces show it as a separate line. Many traders do not look at it.

The blindside works like this. You open a long at $100. Your liquidation threshold is $90 based on mark price. The last traded price on the orderbook is $102, then it drops to $95. You see a 7% move. You think you have 5% of room. But the spot index has already moved to $89, the basis has decayed, and the mark price is $88. You are liquidated. The last traded price on your exchange never reached $90. The orderbook you were watching was the wrong number.

Each exchange's mark price formula changes the exact threshold. On Binance, the spot index weight means a move on a single exchange in the basket has limited effect. On Bybit, the median filters extreme wicks entirely. On dYdX, the time-weighted average means a brief spot spike barely registers. A trader who does not know the formula cannot predict when liquidation hits.

The mark price is not a conspiracy. It is a necessary design choice. Perpetual futures are products that use borrowed funds. A flash crash on one exchange, caused by a fat finger or a coordinated attack, would liquidate thousands of positions if last traded price were used. The mark price insulates the system from that. But it also insulates the trader from seeing their true risk.

You cannot watch the last traded price and know your liquidation distance. You must watch the mark price. You must understand how your exchange calculates it. Binance's mark price moves differently than Bybit's. Bybit's moves differently than dYdX's. The spot index, the basis decay, the weighting scheme - these are not abstract details. They are the difference between a position that survives a wick and one that does not.

The orderbook tells you what someone just paid. The mark price tells you what your liquidation engine sees. They are not the same number. They will never be the same number as long as manipulation is possible. Relying on the last traded price is relying on the wrong signal; the mark price is the one that matters.

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