Rental property calculators, and what each one is for

Three of them, free, for the questions that come up most often: what a property earns before the loan, how far the rent can fall before it stops paying for itself, and what an empty month costs. They run in your browser. Nothing is sent anywhere, nothing is stored, and there is no email address to enter. Each one says plainly what it leaves out.

The question: how far can the rent fall before this property stops paying for itself?

You type the price, the rent, the down payment, the rate, the term and an expense share, and it gives you the rent at which the property covers its loan and its expenses exactly. Everything above that line is margin, and the calculator tells you how much margin you have.

Use it when you are weighing a purchase, or when a lease is up for renewal and you want to know how much room you actually have.

It does not know your real taxes and insurance: it approximates them with the expense share you type. And it assumes twelve months of rent.

The question: what does this property earn before the loan?

Price, rent, expense share. You get the cap rate, the operating income for the year, the rent-to-price ratio and the gross rent multiplier. It ignores financing on purpose, which is what lets you compare two properties that would be financed differently.

Use it to compare properties, or to sanity-check an asking price against what the building actually produces.

It does not say anything about your mortgage, the roof, or whether the current rent is above market. A high cap rate is often a building nobody wants, at a price that says so.

The question: what are these empty days costing, and is a rent cut cheaper?

Rent, days empty, turnover and leasing costs, and the cut you are weighing. It gives you the rent that did not arrive, what the vacancy has cost all in, what each empty day costs, and then the number the decision turns on: a year of the lower rent, expressed as days of full rent.

Use it when a unit has been listed for weeks and you are arguing with yourself about the price.

It does not add your mortgage payment to the lost rent, which many vacancy calculators do. That counts the same money twice, and the inflated figure is what makes a bad rent cut look sensible.

A calculator answers one question about one property. Choosing between five listings is a different job, and doing it in five browser tabs is how people end up trusting none of the numbers.

The Deal Screener puts five properties on one page with the same arithmetic on each: monthly cash flow, cash-on-cash return, cap rate, cash needed to close, and how far the rent can fall before each one breaks even. It opens in Excel and in Google Sheets, every formula is readable, and it is free.

Each formula in it is checked against a second calculation written separately from the spreadsheet, and what those checks have caught is written out in How We Test.