Compute net cash flow on a short-term rental factoring in cleaning, platform fees, and STR-specific operating costs.
Net monthly cash flow
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Gross monthly revenue
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Cash-on-cash return
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Cap rate
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Effective nights/month
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Why a high nightly rate fools first-time hosts
A short-term rental advertises a number that looks irresistible. Two hundred dollars a night across thirty nights reads like $6,000 a month, several times what the same house would fetch on a yearly lease. Then reality arrives. The unit is not booked every night, the platform skims its cut off the top, every guest turnover triggers a cleaning bill, and the utilities, supplies, and wear run far above a long-term tenant who pays their own power and stays for years. By the time those costs land, the gap between an Airbnb and a traditional rental is often a fraction of what the gross suggested. This calculator forces all of that into the open before you sign.
It works in monthly terms. Occupancy times an average month of 30.4 days gives your booked nights. Booked nights times the nightly rate gives gross revenue. From that it subtracts the platform fee, a cleaning cost tied to how often guests turn over, the monthly slice of your annual taxes and insurance, and a catch-all for everything else. What remains is net operating income, and once the mortgage comes out you have the number that actually hits your bank account.
A $350,000 cabin, booked 70% of the time
Picture a $350,000 property bought with $90,000 down and closing, carrying an $1,800 monthly mortgage. You list it at $200 a night and run 70% occupancy, pay a 15% platform fee, $90 per cleaning turn, $5,000 a year in taxes and insurance, and $350 a month in other costs. The tool walks it like this.
| Line item | Monthly |
|---|---|
| Booked nights (30.4 x 70%) | 21.3 nights |
| Gross revenue (21.3 x $200) | $4,256 |
| Less platform fee (15%) | $638 |
| Less cleaning (turns x $90) | $639 |
| Less taxes, insurance, other | $767 |
| Net operating income | $2,213 |
| Less mortgage | $1,800 |
| Net cash flow | $413 |
That $413 a month annualizes to roughly $4,950, a cash-on-cash return near 5.5% on the $90,000 invested, with a cap rate around 7.6%. The headline $6,000 of gross revenue became $413 of real profit. Drop occupancy to 55% in a slow season and that cushion vanishes entirely, which is the scenario every host should stress-test before buying.
The taxes a cash-flow calculator cannot see
Short-term rental taxation is its own discipline. If the average guest stay is seven days or fewer, the IRS does not treat the activity as a passive rental at all, which changes how losses are handled and can pull the income out of Schedule E and onto Schedule C, exposing it to self-employment tax if you provide substantial services like daily cleaning or meals. There is also the much-discussed "STR loophole," where material participation in a property with short average stays can let losses, including bonus depreciation from a cost segregation study, offset your W-2 or business income. That is genuinely powerful and genuinely easy to get wrong. Treat the cash flow this tool produces as the operating picture, and bring a CPA into the tax picture before you assume any paper loss is usable.
How should I handle occupancy in year one?
Be pessimistic. A brand-new listing with no reviews ranks poorly in search and converts worse than an established one, so first-year occupancy commonly runs 10 to 20 points below the market average you see on AirDNA. Model year one at a conservative occupancy and a steady-state year separately, and make sure the property survives the weaker number, because that is the year your reserves get tested.
Why does the cleaning cost scale with nights?
Because cleaning is a per-turnover expense, not a flat monthly one. The calculator assumes an average stay of three nights, so it divides your booked nights by three to estimate the number of guest turnovers, then multiplies by your cleaning fee. If your guests typically stay a week, you have fewer turnovers and lower cleaning cost, so a tool that hard-codes a flat cleaning bill will overstate this line for you.