# Back-Of-The-Envelope Calculation

## DEFINITION of 'Back-Of-The-Envelope Calculation'

An informal mathematical computation, often performed on a scrap of paper such as an envelope. A back-of-the-envelope calculation uses estimated and/or rounded numbers to quickly develop a ballpark figure. The result should be more accurate than a guess, but will be less accurate than a formal calculation performed using precise numbers and a spreadsheet or calculator.

## BREAKING DOWN 'Back-Of-The-Envelope Calculation'

Back-of-the-envelope calculations might be used to determine whether further research and more detailed calculations are warranted. For example, an investor might look at a company's annual report and do a back-of-the-envelope calculation to get its price-to-earnings ratio. If it is low enough to imply value, the investor can do a proper calculation which might include factoring in the weighted average shares outstanding for the year. If the quick estimate gave a high P/E ratio, time could be saved.