What is Perpetuals mark price？

Mark price is the fair price for perpetuals market to calculate unsettled P&L of positions and generate real-time funding rates.
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Calculation of mark price

BIT's mark price is derived from both the index price and the fair price as follows:
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Mark Price = Index Price + 30 seconds EMA* of (Fair Price - Index Price)
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*EMA: An exponential moving average (EMA) is a type of moving average (MA) that places a greater weight on the most recent data points. The exponential moving average is also referred to as the exponentially weighted moving average.
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Fair Price = (Fair Impact Bid + Fair Impact Ask) / 2
Fair Impact Bid = The average price at which Impact Notional worth of contracts can be bought
Fair Impact Ask = The average price at which Impact Notional worth of contracts can be sold
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Impact Notional is used to determine how deep in the order book to measure the Fair Impact Bid/Ask price. The Impact Notional amount is set to be, e.g. 10,000USD for BTCUSD Perp, 3,000USD for BCHUSD Perp, and in the range of 1,000 to 3,000USD for other USD-Margined contracts.
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Fair Price can never be 5% higher than the best ask or 5% lower than the best bid, and Mark Price is limited within 0.5% from Index Price against manipulative trading.
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The Impact Notional and price limits might be adjusted by the BIT risk team according to market conditions.
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How to check the mark price

Mark price is slightly different from index price, you could track the real-time mark price on the top of the contract trading page.