Index Price Calculation
Perpetual Contract
What is an Index Price?
The index price is one of the most important reference prices in futures trading. It is calculated by aggregating the trading prices of multiple top-tier spot exchanges, weighted by each exchange's trading volume. The index price reflects the fair market value of a crypto asset globally and serves several purposes:
- Calculate Price: It helps determine the mark price, which is used to calculate unrealized P&L and margin requirements.
- Reduce Manipulations: Prevents the price of a single exchange from disproportionately affecting futures pricing and reduces the impact of volatility on a single market.
- Trading Reference: Provides an objective, market-recognized reference asset price.
On the XT platform, the index price is not only an essential reference for traders but also important to mark price calculation and risk management.
Where to View Index Prices
On the XT platform, go to the USDT-M or Coin-M Futures trading page. The real-time index price of the asset is displayed at the top:
Alternatively, click [Futures Info] → [Futures Index] to open the Futures Index page:
Here you can:
- View the index price of the asset over different periods.
- Check other assets' index prices.
- Check historical index price changes at the bottom of the page.
How is the Index Price Calculated?
The index price is determined by two main variables:
- Spot Price: The real-time market price of the asset from major spot exchanges.
- Real-Time Weight: Based on the 24-hour trading volume of the asset on each exchange. Higher volume means higher weight and more influence on the index price.
The calculation of the index price on XT:
Index Price = (Spot Price on Exchange A × Weight of Exchange A) + (Spot Price on Exchange B × Weight of Exchange B) + (Spot Price on Exchange C × Weight of Exchange C) + …
Where the weight of a specific exchange is calculated as:
Weight of Exchange = 24-hour trading volume of the asset on that exchange ÷ Total 24-hour trading volume across all included exchanges
- Example
Suppose the BTC spot prices and volumes on several exchanges are as follows:
| Exchange | Pair | Spot Price | Weight |
| XT | BTC/USDT | 113,079.50 | 20% |
| B | BTC/USDT | 113,070.90 | 15% |
| C | BTC/USDT | 112,998.80 | 15% |
| D | BTC/USDT | 113,128.00 | 10% |
| ... | BTC/USDT | 113,032.90 | 40% |
With XT’s weight at 20%, the index price is calculated as:
(103,079.5 × 20%) + (103,070.9 × 15%) + (112,998.8 × 15%) + (113,128.0 × 10%) + (113,032.9 × 40%) = 113,051.9