Cotton is the best material for making bedsheets. The fabric makes the bedsheets breathable, which also makes cotton the coolest material for bedding material. There are several bedsheets, all made of cotton, that could also differ for breathability. It depends on some properties other than the nature of the fabric. Thread count is one of those properties. Though the bed sheets with higher thread count are considered best, they are generally less breathable than bedsheets with lower thread count. So, an optimum range should be preferred, which stands out for both the qualities. The range of 300-500 is considered best for quality as well as breathability.