DSCR Calculator

The loan that looks at the building, not at you

Most mortgages are a judgement about a person. Payslips, tax returns, employment history, an assessment of whether you personally can keep up the payments. That works well if you have a salary and awkwardly if you are self-employed, own several properties already, or hold everything through a company.

So a different kind of lending exists for investment property, and it asks a different question: never mind the borrower, can the building pay for itself? The debt service coverage ratio is how that question gets answered. It compares the income a property produces against the annual cost of the loan against it. This calculator builds both sides from the raw figures, which is more useful than it sounds, because most of the errors in this calculation happen while assembling those two numbers rather than dividing them.

Building the net operating income

The top half of the ratio is net operating income, and the tool constructs it from three inputs.

Gross operating income is the full annual rent the property would produce with every unit occupied and everyone paying. Vacancy loss is what you deduct for the reality that this does not happen: units sit empty between tenants, and some rent goes uncollected. Operating expenses is the annual cost of running the property, which means property taxes, insurance, management, maintenance, utilities you cover, and repairs.

Subtract the second and third from the first and you have net operating income. One thing to be careful about: the mortgage payment does not belong in operating expenses. It goes in the bottom half of the ratio, and including it in both places is the most common way this calculation gets quietly wrong. Depreciation stays out too, since this is a cash test rather than an accounting one.

Vacancy gets its own line rather than being folded into expenses for a reason, and it is the subject of a section further down, because it is the input people are most tempted to be optimistic about.

Turning a loan into a yearly cost

The bottom half is annual debt service, and rather than asking you for it, the tool works it out from the loan amount, the loan term in years, and the interest rate.

It runs the standard mortgage payment calculation, working out what you would pay each month to clear the loan over the term, then multiplies by twelve to get the yearly cost. That figure includes both principal and interest, which is the correct basis, since both leave your account every month whatever the accountants call them.

Having the tool build this is genuinely useful when you are comparing scenarios. Change the term, change the rate, change how much you borrow, and you see the coverage move immediately, which is exactly the sort of poking about that leads to a deal that works.

A property that just misses

Take a building that would bring in 180,000 a year fully let. Allow 12,000 for vacancy and uncollected rent, and 63,000 for running costs. Net operating income comes to 105,000.

Now finance it with 1,100,000 over 25 years at 6.5 percent. The annual debt service works out at about 89,127, and the coverage ratio is 1.18.

The property is covering its loan with room to spare, which sounds fine. Against most commercial lenders' usual floor of 1.20 to 1.25, it is not fine, and the application would likely come back asking for changes. That is worth showing honestly, because a deal landing just under the bar is a far more common situation than a comfortable pass, and knowing it before you apply is the whole point of running the numbers first.

Working backwards to the loan you can actually get

When a deal falls short, the useful move is to stop asking whether it passes and start asking what would make it pass. The ratio can be run in reverse, and this is how lenders size loans in the first place.

Start from the lender's threshold. At 1.25, the maximum annual debt service this property can support is its net operating income divided by 1.25, which is 84,000. Then ask what loan produces that yearly cost at the same rate and term. The answer is roughly 1,036,700, meaning the borrower would need to bring about 63,300 more to the table than they had planned.

That is the mechanism worth internalising. The income of the building sets a ceiling on the loan, independent of what the building costs or what you would like to borrow. A lender does not start from your request and check it, they start from the income and work down. So if a deal is short, the levers are the ones that move those two numbers: a larger deposit, a longer term to reduce the annual payment, a better rate, or a property whose income genuinely supports the price.

Two gates, and only one of them is about the price

There is a second constraint sitting alongside this one, and understanding how the pair interact explains a lot of otherwise confusing lending decisions.

Loan-to-value caps your borrowing based on what the property is worth. Coverage caps it based on what the property earns. Both apply at once, and the loan you are offered is the smaller of the two, because a lender is not going to waive either.

Which one binds tells you something real about the deal. If loan-to-value is the constraint, the property is priced reasonably against its income and you simply need more deposit. If coverage is the constraint, the property is expensive relative to what it actually produces, and no amount of deposit changes that underlying fact, only how much of the gap you are personally funding. In hot markets where prices run ahead of rents, coverage is very often the binding gate, and investors who only ever check loan-to-value are repeatedly surprised by it.

The line that quietly decides the deal

Of all the inputs, vacancy loss is the one most likely to be filled in hopefully, and it deserves the most scepticism.

Watch what it does in the example above. Vacancy was set at 12,000, giving coverage of 1.18. Double it to 24,000, which is hardly a catastrophe for a property with several units, and net operating income falls to 93,000 while debt service does not move at all. Coverage drops to 1.04. The deal goes from marginal to barely covering itself on one assumption, and it is the assumption with no invoice behind it.

This is why lenders apply their own vacancy figure rather than accepting yours, usually based on the local market rather than your optimism, and why a coverage cushion exists at all. The gap above 1.00 is not a nicety, it is the room for exactly this: a tenant leaving, a rent going uncollected, a roof needing work in a bad year. Fixed loan payments do not adjust when any of that happens.

So the honest way to use this tool is to run it more than once. Enter your realistic case, then enter a bad one, with higher vacancy and higher expenses, and see whether the deal still stands. If it only works when everything goes right, it is not a deal that works. As always, this gives you an educational estimate from the figures you enter, and a lender will rebuild both halves to their own standards before deciding anything.

Questions people ask

How is DSCR calculated?

Divide net operating income by annual debt service. Here, net operating income is gross rent less vacancy loss and operating expenses, and debt service is the yearly principal and interest on the loan.

What DSCR do lenders require?

Commercial lenders commonly want 1.20 to 1.25 or better. Investor loans on residential property sometimes accept 1.0 to 1.20, and some programmes go lower in exchange for a larger deposit, stronger credit, and bigger cash reserves.

Do I include the mortgage in operating expenses?

No. The mortgage is the debt service on the bottom of the ratio. Putting it in operating expenses as well would count it twice and understate the result badly.

What does a DSCR below 1 mean?

The property does not generate enough income to cover its loan payments, so the shortfall comes out of your pocket each year. Most lenders will not proceed without significant compensating strength.

References

The construction of net operating income and the use of coverage thresholds in property lending come from the sources below.

1. Office of the Comptroller of the Currency. Comptroller's Handbook: Commercial Real Estate Lending (net operating income, debt service coverage, vacancy assumptions, and loan-to-value in underwriting). occ.gov
2. Appraisal Institute. The Appraisal of Real Estate (the income approach, effective gross income, vacancy and collection loss, and net operating income).