What Is the Mark Price of Perpetual Contracts? How Is It Different from the Last Price?
Key Takeaway: The Last Price Determines Your Entry Cost, the Mark Price Determines Whether You Get Liquidated
The last price is the real-time price of the most recent trade on the contract, directly reflecting the current market bid-ask battle. The mark price is a "fair value estimate" calculated by the exchange, smoothed out, and specifically used to calculate unrealized P&L and trigger liquidation.
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The core difference is:The last price tells you "how much it costs to trade right now," while the mark price tells the system "what your position is worth and whether it should be liquidated."
1. How Are the Last Price and Mark Price Calculated?
Last Price
The last price is the price of the most recent trade on the perpetual contract, updating with each trade. However, it has a problem: the contract market has its own supply and demand, so the last price may deviate from the true spot price of the underlying asset, and the larger the contract trading volume, the more pronounced this deviation becomes.
Mark Price
The calculation of the mark price is more complex, with the core purpose being "anti-manipulation" and "volatility smoothing." While specific algorithms vary by exchange, the common logic is to take the median of three prices:
| Price Source | Description |
|---|---|
| Index Price | Weighted average of spot prices from multiple major exchanges, reflecting the "true" value of the asset |
| Price Adjusted with Funding Rate | Index price × (1 + current funding rate × time until next settlement) |
| Price Adjusted with Basis Moving Average | Index price + 5-minute moving average of the spread between the mid-market price and the index price |
For most platforms like OKX and Bybit, the mark price = median(Price 1, Price 2, Last Price). Using the median helps exclude extreme values, preventing abnormal single price sources from affecting the mark price calculation.
There are also subtle differences between exchanges. For example, OKX's mark price is closer to the spot price with a faster response to fluctuations, while Binance adopts a more conservative approach with a lower tolerance for deviation from the index price (±2% vs. OKX's ±5%).
2. Why Is the Mark Price Used to Determine Liquidation?
If the last price were used to determine liquidation, this scenario could occur:An extreme trade price ("wick") appears in the market for a short period, causing your position to be liquidated even though the spot price of the underlying asset never reached that level.This is the core reason for the mark price—to prevent unfair liquidations.
| Dimension | Last Price | Mark Price |
|---|---|---|
| Used For | Opening, closing, realized P&L | Unrealized P&L, liquidation trigger price |
| Stability | Highly volatile, affected by single trades | Smooth and stable, anti-manipulation |
| Calculation Basis | Actual trades on the contract order book | Index price + funding rate + basis moving average |
When you see your unrealized P&L fluctuating, it is calculated using the mark price. Whether liquidation is triggered also depends on whether the mark price hits your liquidation price.
3. Practical Tips
Opening and closing positions are executed at the last price.The price of your limit or market order is the actual trade price on the order book, not the mark price.
Do not treat the spread between the mark price and the last price as an arbitrage opportunity.A difference between them is normal and by design; it does not represent a risk-free arbitrage. A larger spread indicates a greater deviation between the contract market and the spot market, and the funding rate mechanism will drive prices back toward convergence.
If you notice a sudden widening of the spread between the mark price and the last price, it usually means the market is experiencing extreme volatility. In such cases, the risk of liquidation increases—even if the last price has not yet reached your liquidation level, the mark price might have. When trading, it is advisable to monitor both prices rather than just one.
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4. How to Check
In the "K-line" or "Depth" area of the trading interface, you can usually see the "Last Price" and "Mark Price" displayed side by side. Some platforms label the mark price as "Mark Price" or "Fair Price" and show it separately near the liquidation price. If the unrealized P&L you see on your position page differs from the value calculated using the last price, this is normal—the former uses the mark price, while the latter is just your estimate. What truly determines whether you receive a liquidation notice is the mark price.
