Mark Price, Last Price & Index Price

TTT perpetual markets use multiple price references to support:

• Fair liquidation mechanics;
• Accurate PnL calculation;
• Stable funding settlement;
• Manipulation-resistant trading infrastructure.

The three primary price references are:

• Last Price;
• Mark Price;
• Index Price.

Each price serves a different function inside the perpetual trading system.

Last Price

The Last Price is the most recent executed trade price on the orderbook.

This is the actual market execution price generated when:

• A buy and sell order match;
• A trade is filled on the matching engine.

The Last Price continuously changes based on real-time market activity and orderbook liquidity.

The Last Price is primarily used for:

• Market activity display;
• Candlestick charts;
• Recent trade history;
• Orderbook execution visibility.

Because the Last Price can be affected by:

• Temporary volatility;
• Thin liquidity;
• Short-term price spikes;

it is not used as the primary liquidation reference.

Index Price

The Index Price represents the estimated fair spot market value of the underlying asset.

It is typically derived from aggregated spot market prices across multiple external exchanges and liquidity sources.

The Index Price acts as the external market benchmark used by the perpetual pricing engine.

The Index Price is primarily used for:

• Fair market valuation;
• Funding rate calculations;
• Mark Price calculation;
• Reducing isolated exchange price deviations.

Example:

• BTC spot prices from multiple exchanges may be aggregated into a single BTC Index Price.

Mark Price

The Mark Price is the fair-price reference used internally by the perpetual trading engine.

It is derived using:

• The Index Price;
• Funding basis adjustments;
• Market premium calculations.

The Mark Price is designed to reduce unfair liquidations and prevent temporary market manipulation from affecting core risk calculations.

The mark price is used for:

• Unrealized PnL calculation;
• Liquidation checks;
• TP/SL trigger evaluation.

By default, TP/SL orders use the Mark Price as the trigger condition, but users can optionally switch the trigger type to Last Price.

Because the Mark Price reflects a more stable and manipulation-resistant valuation, it is generally more reliable for liquidation and risk management infrastructure than the Last Price alone.

Example

Example market state:

In this example:

• The Last Price reflects the latest executed trade;
• The Index Price reflects the broader external market value;
• The Mark Price reflects the internal fair-price reference used by the risk engine.

Even if the Last Price temporarily spikes due to volatility or low liquidity, liquidation and margin calculations continue using the Mark Price to reduce unfair liquidations.