Rental Cash-Flow Calculator
A rental property either pays you every month or quietly costs you money. This calculator separates the two before you buy. Enter the rent and every real monthly cost — including the reserves most spreadsheets leave out — and see monthly cash flow, annual cash flow, and cash-on-cash return on the capital you put in.
Estimate — illustrative only. Not a quote, an approval, or investment advice. Defaults are common planning assumptions, not RECR figures; replace every field with your own numbers and confirm actual rent, taxes, insurance, and financing costs before you rely on any result.
What the Number Actually Tells You
Monthly cash flow is what is left after the property pays for itself. It is rent minus every recurring cost of owning and operating the unit: the mortgage payment, taxes, insurance, any HOA dues, and the three reserves that separate a real projection from an optimistic one — vacancy, maintenance, and management. When that figure is positive, the property carries its own debt and still puts money in your account. When it is negative, you are subsidizing the asset every month and betting entirely on appreciation to bail you out.
The reserves are where most back-of-the-napkin math goes wrong. A property is not rented one hundred percent of the time, it does not maintain itself, and someone has to manage it even if that someone is you. Leaving those three lines out does not make them disappear — it just moves the surprise to the month a tenant leaves, the furnace dies, or your time runs out. Modeling them up front is the difference between a plan and a wish.
- Vacancy reserves for the weeks between tenants and the occasional non-paying month. Five percent is a common starting assumption; soft rental markets warrant more.
- Maintenance covers turns, repairs, and the slow replacement of roofs, systems, and appliances. Older properties carry a higher percentage.
- Management is a real cost even when you self-manage, because your time has value. If you plan to hire out, use the actual quoted rate.
Cash-on-Cash Return
Cash flow tells you whether the property pays. Cash-on-cash tells you whether it is a good use of your money. It is annual cash flow divided by the total cash you actually put into the deal — down payment, closing costs, and any rehab you funded out of pocket. A property that throws off $3,000 a year on $45,000 of invested cash returns roughly 6.7 percent cash-on-cash, before any appreciation, loan paydown, or tax benefit.
That single percentage lets you compare a rental against every other place your capital could sit. It also exposes the quiet cost of a low-leverage purchase: put more cash in and monthly cash flow rises, but cash-on-cash can fall, because the return is now spread across a larger pile of money. The right amount of leverage is a deliberate choice, not an accident — and it is exactly the tension a joint-venture or higher-leverage structure is built to change.
Where financing lets you keep more of your own capital in reserve, the same rent can produce a stronger cash-on-cash figure on the cash you actually deployed. That is the lever this calculator helps you see. Run the debt-service side of the same property through the DSCR calculator to check whether the rent also supports the loan a lender would underwrite.
Every Line in the Formula
Nothing hidden. This is exactly what the calculator computes when you change an input.
| Gross monthly rent | $1,800 | What the unit collects when occupied |
|---|---|---|
| Principal & interest (P&I) | $820 | The mortgage payment on your financing |
| Property taxes | $220 | Monthly share of the annual bill |
| Insurance | $95 | Landlord / hazard coverage |
| HOA / condo dues | $0 | Where applicable |
| Vacancy (5% of rent) | $90 | Reserve for empty months |
| Maintenance (5% of rent) | $90 | Repairs and capital reserve |
| Management (8% of rent) | $144 | Operating cost, even if self-managed |
| Monthly cash flow | $341 | Rent minus every cost above |
| Annual cash flow | $4,092 | Monthly cash flow × 12 |
| Cash-on-cash (on $45,000 in) | 9.1% | Annual cash flow ÷ cash invested |
Change one input and watch the chain move. Drop the rent by $150 and the reserves fall slightly while the payment stays fixed — cash flow compresses fast, because the costs are mostly rigid and the rent is the only elastic line. That sensitivity is the whole reason to model a rental before you own it, not after. A deal that clears by $341 a month has room; a deal that clears by $40 does not.
Questions About Rental Cash Flow
Why does the calculator subtract vacancy, maintenance, and management as percentages?
Because those three costs scale with rent and recur forever, but they do not arrive on a neat monthly schedule. Reserving a percentage of every month's rent smooths a lumpy reality: the tenant turn, the roof, the eventual property manager. A projection that ignores them looks great on paper and disappoints in year two.
What is a "good" monthly cash flow?
There is no universal number — it depends on the price of the property, your market, and your goals. What matters is that the figure is positive after real reserves, and that it leaves enough room to absorb a bad month without forcing a sale. Thin positive cash flow on paper can turn negative the first time a major system fails.
How is cash-on-cash different from cap rate?
Cap rate measures the property's unleveraged return — net operating income divided by price, ignoring the loan. Cash-on-cash measures your return on the actual cash you invested, after financing. The two diverge the moment you use leverage, and cash-on-cash is usually the more useful number for an investor deciding where to put a limited amount of capital.
Should I include principal paydown or appreciation here?
No. This tool measures spendable cash flow only, which keeps it honest. Principal paydown builds equity but you cannot spend it monthly, and appreciation is a forecast, not a cash flow. Both are real parts of total return — they just belong in a separate calculation, not in the number that tells you whether the property pays its own bills.
Does financing structure change my cash flow?
Directly. The P&I line is set entirely by how the purchase is financed, and the cash-invested figure driving cash-on-cash is set by how much of your own money the structure requires. Keeping more capital in reserve rather than in the deal can raise cash-on-cash on the money you actually deployed. See how a rental fits RECR's rental and DSCR financing.
Can I use this for a property I plan to flip, not hold?
Not usefully — a flip is a one-time profit event, not a monthly income stream. For a resale project, model the spread between purchase, rehab, and after-repair value instead, using the fix-and-flip deal analyzer. Use this calculator when the exit is to rent and hold.
Rental Numbers That Work?
If the cash flow and cash-on-cash hold up, the next step is financing that keeps the return strong. Send the property, the rent, and your numbers for a first read.