Debt service cover calculator

How many times your income covers the annual debt service — the test almost every commercial lender applies before sizing a loan. Works from rent or from trading profit, interest-only or capital and interest, and at a stressed rate rather than the rate you are quoted.

Fill in the income, the loan amount and the rate, and the figure appears here. Nothing is sent anywhere — the whole calculation runs in your browser.

The things that change the answer

It is two different tests, not one

On an investment property, cover is measured against rent, usually with a deduction for voids, and usually interest-only. That is normally called ICR. On a business you run, it is measured against adjusted net profit and against the full debt service including capital. That is normally called DSCR. They are not interchangeable and the same deal can pass one and fail the other.

InterBay publish both, and for an owner-occupier they apply two tests at once — 125% against net profit or EBITDA, and 110% against the market rent a valuer confirms.

Lenders test at a stressed rate, not your rate

InterBay’s published rule is an interest cover ratio based on “5%, or the initial pay rate — whichever is higher”. So a cheap rate today does not help you: the test runs at the floor. Enter a stress floor above and you will see the difference it makes.

Interest-only versus capital and interest is the biggest single lever

£80,000 of profit against a £500,000 loan at 7.5% covers the debt 2.13 times interest-only, and 1.65 times on a twenty-year repayment basis. Nothing about the property or the business changed — only how the loan is structured.

The same test gets published upside down

InterBay express it as a coverage ratio: income must be at least 125% of the debt service. Together express the reciprocal: “total secured debt payments should not exceed 50% of the customer’s net income/profit”. Those are the same kind of test pointing in opposite directions — 50% of profit is cover of 2.00 times, and their 75% referral ceiling is cover of 1.33 times. This calculator gives you both figures so you can meet whichever form the lender in front of you uses.

Why there is no “typical minimum” here

Because there is no honest one. Of four UK lenders checked on 26 August 2026, InterBay and Together publish their tests openly; Shawbrook and Cambridge & Counties publish loan sizes and loan-to-value but keep the cover ratio in criteria documents they do not put on the open web. Any “market average” assembled from public sources therefore describes a self-selected half of the market and quietly presents it as the whole.

So this page shows you named lenders’ own published tests, links to them, and dates them. Your lender sets its own figure. Ask them for it.

How the arithmetic works

Debt service on a repayment loan uses the standard annuity formula, on the monthly rate over the whole term, and is rounded up to the penny — which nudges the cover ratio very slightly down. That is deliberate: a calculator that rounds a borrower’s cover upward is telling them a deal clears a threshold it may not. Interest-only debt service is simply the loan multiplied by the rate. Cover is income divided by debt service; the percentage shown alongside it is debt service divided by income.

This is a calculator, not advice, and it does not account for arrangement fees, other secured borrowing, personal guarantees, or covenants your lender may apply beyond the cover ratio.