Short interest is the ratio of short interest to float, expressed as a percentage. Short interest refers to the number of shorted shares for a particular stock. The float of a stock is the number of outstanding shares available for trading. The ratio can also be expressed as the number of days to cover, which is the total short position divided by the average daily trading volume. High short interest ratios typically indicate bearish market sentiment, Short interest as a percentage of float above 10% is fairly high, indicating significant pessimistic sentiment. Short interest as a percentage of float above 20% is extremely high.