About Nifty Oil & Gas The Nifty Oil & Gas Index is designed to reflect the performance of companies in the oil, gas, and petroleum sectors. It comprises a maximum of 15 tradable, exchange-listed companies. The index is computed using the free float market capitalization method, where the level of the index reflects the total free float market value of all the stocks in the index relative to a particular base market capitalization value. The index can be used for various purposes such as benchmarking fund portfolios, launching index funds, ETFs, and structured products.