Sep 25, 2013 · Like other ratios, you should compare the P/S of a stock of those with competitors and with historical sales multiples. buying back stock and paying dividends. As editor of the Forbes 15 Financial Ratios Every Investor Should Use Price Ratios. Price ratios are used to get an idea of whether a stock 's price is reasonable or not. They are easy to use and generally pretty intuitive, but do not forget this major caveat: Price ratios are "relative" metrics, meaning they are useful only when comparing one company's ratio to another company's ratio, a company's ratio to itself over time, or a company's ratio to a benchmark.