Run the numbers before you make an offer
Property listings sell a feeling. Spreadsheets sell the truth. A house that looks like a bargain at $300,000 can lose money every month once taxes, insurance, repairs, vacancy and loan payments land. A short-term rental that seems to print cash can flop in the off season.
The eight calculators here cover rentals, flips and tax strategy. They run in your browser and keep your numbers private.
Measuring a rental: yield, cap rate and cash-on-cash
Three ratios get used constantly, and they answer different questions.
Rental yield is annual rent divided by property value. Gross yield ignores costs. Net yield subtracts them. The rental yield calculator shows both, plus a breakdown of how each cost eats into income.
Cap rate is net operating income divided by price. NOI is rent minus vacancy and operating costs, before any mortgage. The cap rate calculator builds NOI from gross rent and vacancy, and has a reverse mode: enter the cap rate you want and it tells you the price to pay. It draws a waterfall and a yield spectrum so you can see where the deal sits.
Cash-on-cash return measures the cash you actually put in against the cash you get back, after mortgage payments. It's the most honest number for buyers who borrow. A deal with a 6 percent cap rate can return 10 percent cash-on-cash with the right loan, or 2 percent with a bad one.
Rental property ROI over time
The rental ROI calculator looks across multiple years. It tracks cash flow, mortgage paydown, appreciation and selling costs, then reports total and annualized ROI. A sensitivity grid shows what happens if rent, vacancy or appreciation come in lower, and a pie shows how your wealth is made up.
Appreciation is the shakiest piece. Don't build a deal on it. If a property only works when prices rise 5 percent a year, it doesn't work.
Selling costs matter too. Agent fees and closing can take 6 to 10 percent of the price, which hurts if you sell after a short hold.
Short-term rentals
The Airbnb profit calculator accounts for seasons. Enter occupancy for each month, nightly rates, platform fees, cleaning costs and fixed costs. It returns net profit by month and for the year.
Occupancy is where most estimates fail. Look at real comparable listings, not the host with the best photos. And check local rules. Many cities limit short-term rentals or require permits, and some ban them in certain buildings.
Cleaning, supplies, furnishing and your own time cost more than first-timers expect. If a manager takes 20 percent, include it.
Flips and BRRRR
The house flipping calculator takes purchase price, rehab line items, interest carry, closing costs and sale costs, and tests your after-repair value. It checks your deal against the 70 percent rule: pay no more than 70 percent of ARV minus repairs. The rule is a guardrail, not a promise. In pricey markets few flips fit it.
Rehab always costs more and takes longer. Add a 10 to 20 percent cushion. Each extra month of carry costs interest, taxes and insurance.
BRRRR stands for buy, rehab, rent, refinance, repeat. The simulator tracks how much capital you pull back out at refinance, the debt service coverage ratio, post-refi cash flow and how many deals one pile of cash can fund. The plan only works if the appraisal comes in near your after-repair value. Lenders also often limit cash-out to a percentage of value, so don't assume you'll recover everything.
1031 exchanges
A 1031 exchange lets you defer capital gains tax when you swap an investment property for a like-kind one. The calculator estimates boot (cash or debt relief that's taxable), 25 percent depreciation recapture, long-term capital gains rates, the net investment income tax and the minimum replacement value you need to defer everything.
The timelines are strict. You have 45 days to identify a replacement and 180 days to close, and a qualified intermediary has to hold the funds. Miss a deadline and the tax bill arrives. Get a tax professional involved before you sell.
A sanity checklist
Use conservative rent. Use realistic vacancy, 5 to 10 percent in many markets. Include repairs and capital expenses even when the building looks fine. Test your interest rate plus two points. If the deal still works, you've found a margin of safety.
These are estimates. Local taxes, laws and market conditions change results.