Rental Cash Flow and Cap Rate Calculator

Most rental spreadsheets show a profit because they omit three things: vacancy, ongoing maintenance, and capital reserves for the roof and the furnace that will eventually need replacing.

Leaving them out does not make them go away — it just moves the loss to a year you did not plan for. The calculator below includes all three.

The two lines people delete

Maintenance and capital reserve. They feel optional because nothing breaks most months, and then a $9,000 roof arrives in a year that had already been spent. A property that only works when those lines are zero does not work.

Self-managing is not free

Setting the management line to zero because you do it yourself is fine for cash flow, but note what it means: you have bought yourself a job. If you would ever hire out, run the numbers again with 8–10% of rent and check the deal still stands.

Cap rate versus cash-on-cash

Cap rate describes the property. Cash-on-cash describes your deal, including the loan. Two investors buying the same building at the same price can have very different cash-on-cash returns — and only one of those numbers is comparable across listings.