Calculating an interest rate To calculate an interest rate, you'll need a few pieces of information: The interest expense, which you can find on a company's income statement.

If your business makes investments in equipment and employee benefit contributions, you may need to track the average annual rate of return over a span of time for financial reporting obligations.

Calculate the weighted average of interest rates in Microsoft Excel to compute the most accurate average interest rate among a group of lenders who received different rates.

You can find information about a company's debt and how much interest it pays to service its debt, but the actual interest rate it pays is generally not included in its financial statements.