Definition: An interest expense is the cost incurred by an entity for borrowed funds. Interest expense is a non-operating expense shown on the income statement. It represents interest payable on any borrowings – bonds, loans, convertible debt or lines of credit. It is essentially calculated as the interest rate times the outstanding principal amount of the debt. Interest expense on the income statement represents interest accrued during the period covered by the financial statements, and not the amount of interest paid over that period. While interest expense is tax-deductible for companies, in an individual's case, it depends on his or her jurisdiction and also on the loan's purpose.

In Plain English: Interest is an expense that you must pay in addition to the amount of money borrowed.

Example: If you took out a loan to start your shoe business in the terms of that loan there would be an interest rate. This would be used to calculate the interest expense as a percentage of the principal amount of the loan outstanding and would be added to the loan payment each month.

The amount of interest expense has a direct bearing on profitability, especially for companies with a huge debt load. Heavily indebted companies may have a hard time serving their debt loads during economic downturns. At such times, investors and analysts pay particularly close attention to solvency ratios such as debt to equity and interest coverage.