Cost of Debt for a Small Business: What to Calculate Before Changing a Loan

Choose the question before the formula

“What is our cost of debt?” can mean several different things. An accountant may be summarizing interest expense for a reporting period. An owner may want to know the dollars still payable on one loan. A financing adviser may be comparing a new offer with the current agreement. One percentage cannot answer every question.

For a practical management review, keep three boxes: historical interest burden, future financing costs and cash required for repayment. This guide helps you fill those boxes. It does not replace the detailed cash-flow comparison in the loan analysis guide or the complete business loan cost reduction plan.

Build a historical interest indicator

An indicative historical interest rate can be calculated as interest expense for the period divided by average interest-bearing debt for that same period. If the period is a full year, the result describes that year's relationship. For a shorter period, show the dates and avoid presenting the number as an annual rate without a stated annualization method.

Use average balances that reflect borrowing through the period. Monthly balances are more informative than a simple opening-and-closing average when borrowing rises sharply or fluctuates with the season. Include only the interest and debt that belong together. Keep leases, shareholder loans and foreign-currency balances visible, with their accounting treatment confirmed.

This is a management indicator, not a quoted rate, a contractual APR or the cost of a new loan. Cost of debt also appears in cost-of-capital analysis, where tax treatment and the mix of debt and equity matter. ^[1] This worksheet stays before tax; ask your accountant before using a tax-adjusted measure.

Worked example: the same debt, three useful numbers

A fictional restaurant records $18,000 of interest for a full year and calculates $200,000 of average interest-bearing debt from its monthly records. Its historical interest indicator is 9%: $18,000 divided by $200,000. It separately records $2,000 of loan-related fees.

The $20,000 combined interest and fee amount is useful for a cash-cost review, but adding those fees to a ratio does not automatically produce a legally defined APR. Some charges may be recognized in a different accounting period. Reconcile the books and the payment records before combining them.

The restaurant also repays $40,000 of principal during the year. Total cash paid for those three items is $60,000, but the $40,000 principal is repayment of borrowed money, not an interest expense. A business can have manageable interest expense and still face a difficult principal repayment schedule.

Calculate what remains, not just what happened

For an existing facility, obtain a schedule of future interest, fees and principal. Identify charges that depend on a future event, such as renewal, late payment or early settlement. Interest rates alone do not capture every borrowing charge. ^[2]

Suppose the restaurant's current loan has $14,000 of future interest and $600 of future fees. A replacement would have $11,000 of interest, $1,200 of new fees and $1,500 of exit costs. With equal principal and the same final repayment date, the costs are $14,600 versus $13,700, an undiscounted difference of $900. That conclusion changes if payment dates, remaining balances or other charges differ.

Use a consistent comparison period

If one offer repays in two years and another in four, compare both through a common date and include the principal still owed then. A lower amount paid so far may simply mean a larger remaining obligation. Where timing materially affects the choice, ask for a discounted cash-flow comparison with the rate and assumptions stated.

Keep currencies separate unless you use a disclosed conversion date and method. Keep forecasts separate from actual results. A cost-benefit review becomes more useful when both the costs and the benefits refer to a defined period. ^[3] The discipline matters more than displaying a precise-looking percentage.

Complete the worksheet before making a claim

Write the period, debt included, interest expense, averaging method and fees included. Add the current payout quote and the remaining repayment schedule. Record where each number came from. If two statements disagree, resolve the difference instead of averaging away the problem.

Finish with one decision question: is the issue the rate, the fees, the amount borrowed or the payment dates? Follow the relevant guide rather than using the historical ratio as a verdict. A lower ratio next year may reflect a different borrowing mix; it does not by itself prove that a refinancing decision saved money.

Your practical worksheet

Use actual documents to complete each field. Record the source of each number, outstanding questions and your decision. The worksheet is printable and includes space for your notes.

Open the printable worksheet

Frequently asked questions

Is principal repayment part of borrowing expense?

It uses cash and reduces the balance, but it is not interest expense. Show it separately when reviewing the loan.

Should I use a before-tax or after-tax measure?

Use a clearly labelled before-tax view for this worksheet. Tax-adjusted comparisons need your accountant's assumptions and transaction-specific treatment.