Financial ratios measure liquidity, activity, leverage, and profitability of a company as a ratio to be able to compare it to other companies, other sectors, and other times. Financial ratios can be used to find the most profitable sectors of the economy and to find the most profitable companies within those sectors. A company can also be compared to its past performance, to see if certain measures are increasing or decreasing, or not moving at all. For instance, a growing company increases revenues and usually profits, from year to year, but is the company becoming more or less profitable as it grows in size? A financial ratio, such as net profit margin, can provide the answer.
Financial ratios are often used to screen stocks by stipulating that a company's financial ratio be a certain minimum or maximum amount, depending on the investor's objective.
The numerators and denominators of financial ratios come primarily from either the company's balance sheet or its income statement. Many websites that provide stock quotes also provide most of the common financial ratios, so investors rarely have to calculate it themselves, although understanding how financial ratios are calculated helps the investor to understand what they mean and their relative importance as well as understanding how they are limited.
Here is a quick overview of the most common financial ratios, with more detailed information in the following articles:
Financial ratios may not be as useful for finding the best investments as they once were. This is because many, if not most, securities are purchased as part of an index fund, through exchange traded funds or mutual funds. Fund managers buy and sell shares of stock based on whether they are part of the index they are tracking and how they are tracking that index. For instance, if a fund is based on market capitalization of an index, then fund managers tracking that index will buy more of that stock as it increases in price relative to other stocks in the index, regardless of worsening financial ratios. This partly explains why the most popular stocks often have undesirable financial ratios and why many fund managers, such as Warren Buffett, miss out on the best stocks, because they are unwilling to buy stocks with undesirable financial ratios. Likewise, if a stock is removed from an index, then fund managers tracking that index will sell that stock, regardless of financial ratios. Being part of an index amplifies stock price changes that becomes somewhat dependent on how well the index does. Because most people invest by buying exchange-traded funds or mutual funds, how well a security will do will depend on what, and on how many, indexes it composes. When a security is added to an index or when the security increases in price significantly, then it will benefit more being part of an index that it would if it were not part of an index. A security removed from an index because of declining financials will drop faster than if it never composed an index.