# Index Price **What is Index Price?** The index price is based on the latest transaction price of the standard currency pair of the mainstream exchange in the market and the median buy-to-sell median, weighted average, calculated and obtained index price, which can represent the fair market price of the currency pair. **Index Exception Handling** **Removing Invalid Prices:** If any source exchange price is not updated within 40 seconds and significantly deviates from the previous value, we consider it not valid and reset the price for that pair to zero. **Abnormal Price Correction:** When an exchange's price deviates from other exchanges by ±3% of the median deviation of all source exchange prices (including itself), we recalculate its price to the median ±3% of the remaining exchange prices. For example, if the USDT median deviation reaches ±3%, we recalculate that exchange's price to the median ±3% of the sample. This mitigates outliers and ensures index price integrity by adjusting excessively deviating prices. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://whitepaper.nomoex.com/our-product/nomodex/overview-of-perpetual-futures/index-price.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.