Rental Property ROI Calculator
Cash flow, cap rate, and cash-on-cash return. Vacancy and maintenance are included by default — leaving them out is how a bad deal starts looking like a good one.
The property
Assumptions
Financing
Buying cash? Set down payment to 100.
Those expense lines are estimates. Later they're facts.
Once you own it, SmartLeaseFlow connects to your bank, matches deposits to tenants, and sorts what you actually spent into Schedule E categories — so next year you're modelling from your own numbers instead of rules of thumb. Plans start at $12/month.
Three numbers, and what each one is actually for
Cash flow, cap rate and cash-on-cash return get quoted together as though they measure the same thing more or less accurately. They don’t. They answer three different questions, and most of the disagreement about whether a deal is any good comes from two people quoting different numbers at each other.
Cash flow: what lands in your account
Rent, minus vacancy, minus operating costs, minus the mortgage. It’s the only one of the three that corresponds to money you can spend, and it’s the one that decides whether you can hold the property through a bad year. A deal with a beautiful cap rate and negative cash flow is a deal you fund every month out of your salary.
Cap rate: the property, with the financing removed
Net operating income divided by price — and NOI is before debt service. That exclusion is the entire point. Cap rate exists so two properties can be compared independently of how each is financed. A calculator that subtracts the mortgage before computing it returns a number that changes when you change your down payment, which makes it useless for the one job it has. Plenty of them do.
Cash-on-cash: the return on the money you actually put in
Annual pre-tax cash flow divided by cash invested — down payment plus closing costs. It cannot be derived from price and rent alone, which is why this calculator asks for the financing rather than assuming it. It’s the number to compare against what the same money would have done somewhere else.
The assumption that flatters every deal
Twelve months of rent a year. It is the single most common way a spreadsheet turns a marginal property into a good one, and it’s wrong every time — tenants leave, turnovers take weeks, and a unit that never sits empty is a unit you’ve been underpricing.
So vacancy defaults to 5% here, which is about two and a half weeks a year, and maintenance to 8% of collected rent. Both are adjustable and both are rules of thumb rather than forecasts — an older property with original plumbing needs considerably more than 8%. Management defaults to 0%, on the assumption that you’re managing it yourself — but it’s a field rather than a fixed assumption: if you might hand the property to a manager in three years, put the number in now and see whether the deal still works.
If you set either to zero the calculator says so in its results. Not to nag — because a return computed with no vacancy and no maintenance is a different quantity from one computed with them, and three weeks later nobody remembers which one they were looking at.
What this deliberately leaves out
Four things that move real returns a lot, all excluded on purpose:
- Appreciation. Nobody knows. A calculator that includes it is reporting your optimism back to you with a percent sign on it.
- Principal paydown. Real, and it makes your actual return higher than the cash-on-cash figure here. It isn’t cash you can spend this year, so it doesn’t belong in a cash-flow number.
- Depreciation and the tax treatment. Depends on your bracket, your other income, and whether you qualify as a real estate professional. Not something a public calculator can know.
- Capital expenditure. The maintenance reserve covers repairs and turnovers. It does not cover a roof, a furnace, or a sewer line. Those arrive on their own schedule and they are the reason a property that cash-flowed for six years suddenly doesn’t.
A plainer number that names its omissions is more useful than a confident one that hides a new roof inside it.
After you buy, the same arithmetic gets harder
Every figure above is a projection you typed. Twelve months in, the question changes to what the property actually did — and that answer is spread across a bank statement, a shoebox of receipts and your memory of which month the tenant paid late. SmartLeaseFlow reads your bank feed and proposes which tenant each deposit belongs to; you confirm, and it remembers that sender next month. It works whether your tenants pay by Zelle, by check, or in cash you deposit yourself, because it reads the account rather than asking anyone to change how they pay. See how it works.
This is a calculator, not investment advice, and we are not financial advisers. The defaults are conventions rather than predictions about your market. Check the figures against your own numbers before deciding anything.