Short-Term Rental Calculator: Underwrite a Deal in 12 Inputs

Twelve inputs decide a short-term rental deal. Run all twelve on a $585,000 Scottsdale condo and annual cash flow is $397, against the $20,992 a gross-minus-30% shortcut reports.

Twelve inputs decide whether a short-term rental deal works, and the standard free calculator uses about six. Run the short version on a $585,000 Scottsdale condo and it reports $20,992 of annual cash flow. Run all twelve on the same property and the number is $397. The $20,595 gap is not distributed evenly across a long list of small omissions. It sits in six line items, and every one of them is knowable before you make an offer.

Key takeaways

• Twelve inputs decide a short-term rental deal: purchase price, down payment, interest rate, closing costs, furnishing capital, ADR, occupancy, cleaning economics, platform fee, lodging tax treatment, fixed annual carry, and reserve percentage.
• A $585,000 Scottsdale condo underwritten across all twelve inputs produces $397 of annual cash flow and a 0.20% cash-on-cash return, against $20,992 from the gross-revenue-minus-30% shortcut.
• Airbnb's single-fee structure charges most hosts 15.5% of the booking subtotal and is mandatory for any host using property management software, which covers nearly every operator above three doors.
• The 30-year fixed-rate mortgage averaged 6.65% on August 20, 2026 in Freddie Mac's Primary Mortgage Market Survey, and that survey covers owner-occupied purchases, so an investment-property quote sits above it.
• The example deal breaks even at 61.5% occupancy against a 62% assumption, so a 10% miss on either occupancy or ADR converts $397 of cash flow into a $4,810 annual loss.

The 12 inputs a short term rental calculator actually needs

Every input below changes the answer by more than $1,000 a year on a single mid-priced door. Nothing else on a typical underwriting spreadsheet clears that bar, which is why the list stops at twelve.

The same twelve apply whether you are buying the asset or leasing it. MagicBNB's Property Analyzer handles purchase mode with full mortgage and depreciation simulation and lease mode for an arbitrage unit, so an acquisition and a rental-arbitrage deal come out comparable instead of living in two spreadsheets.

Four inputs set the capital stack. Purchase price. Down payment percentage, because the split between 20% and 25% moves both the loan balance and the rate you are quoted. Interest rate and term. Closing costs, which run 2% to 4% of price in most states and are cash you never get back.

One input is the line almost everyone leaves out entirely: furnishing and setup capital. A three-bedroom that sleeps eight needs beds, seating, a stocked kitchen, linens in triplicate, smart locks, cameras at the exterior, and photography. That figure belongs in the denominator of your cash-on-cash return, and leaving it out inflates the return by 15% to 25% on a typical deal.

Three inputs set revenue. Achievable ADR, achievable occupancy, and the denominator you are measuring occupancy against. Calendar nights and available nights are different numbers and they differ by 8 to 15 points on a property with any owner-use or maintenance blocks.

Four inputs set the cost side. Cleaning economics as a net figure rather than a revenue line. Platform fee percentage. Lodging tax treatment. And fixed annual carry, meaning property tax, insurance, HOA, utilities, internet, supplies, and software.

The inputs that feel important and change nothing

Roughly thirty fields on a typical underwriting template move the annual answer by less than $500, and they consume most of the time people spend modeling. Appreciation rate is the largest offender. A 3% versus 4% assumption changes nothing about whether the property covers its own costs in year one, which is the only question a purchase decision actually turns on.

Also skip: rent growth beyond year three, exact depreciation schedules before you own the asset, a monthly seasonality curve when you have no booking history to build it from, loan points modeled to the dollar, and any exit cap rate. Every one of those matters at some point in the hold. None of them determines whether you should buy.

Estimated square footage, projected review count, and photography quality scores show up in a lot of templates. They are inputs to ADR, and you have already entered ADR.

A worked example: a $585,000 Scottsdale three-bedroom

The property carries a 6.30% cap rate and returns $397 in cash flow, which is a deal most spreadsheets would clear and most operators should decline. Here is the full stack.

Capital: $585,000 purchase, 25% down at $146,250, a $438,750 loan at 7.40% over 30 years, closing costs of $17,550, and $38,000 of furnishing and setup. Total cash in at $201,800. Annual principal and interest comes to $36,454.

The 7.40% rate is an assumption, and it deserves a note. Freddie Mac's Primary Mortgage Market Survey put the 30-year fixed at 6.65% on August 20, 2026, down from 6.67% the prior week and up from 6.58% a year earlier. That survey covers owner-occupied single-family purchases at 80% loan-to-value. A non-owner-occupied investment loan prices above it, typically by 50 to 100 basis points, so underwriting a rental at the headline rate understates debt service by roughly $3,000 a year on this loan size.

Revenue: $305 ADR at 62% occupancy across 365 available nights is 226 booked nights and $68,930 of nightly revenue. At an average stay of 3.2 nights that is 71 turnovers. Cleaning fees collected at $185 per stay add $13,135, bringing the booking subtotal to $82,065.

Platform fee comes off that subtotal. Airbnb's service fee page states most hosts on the single-fee structure pay 15.5%, with the structure mandatory for hosts who use property management software. At 15.5% of $82,065 the platform takes $12,720. Cleaners are paid $175 per turn, or $12,425, against the $13,135 collected. Cleaning nets $710 for the year, which is why it belongs in the model as a near-zero pass-through rather than as revenue. Net revenue lands at $56,920.

Operating costs: property tax at Maricopa County's 0.44% effective rate on a $452,800 median home value, per the Tax Foundation's county property tax data, applied to $585,000, is $2,574. Short-term rental insurance at $3,400. HOA at $340 a month, $4,080. Utilities and internet at $310 a month, $3,720. Consumables at $1,140 and the software stack at $1,740. A maintenance and capital reserve of 6% of net revenue adds $3,415. Total operating cost: $20,069.

NOI is $36,851. Subtract $36,454 of debt service and annual cash flow is $397. Cash-on-cash return on $201,800 invested is 0.20%. The cap rate reads 6.30% and looks respectable, which is exactly the trap: cap rate ignores the loan and the furnishing capital, and both of those are where this deal actually lives.

Hand the property to a full-service manager at 20% of net revenue and the $397 becomes a loss of $10,987. Self-management is not a preference on this deal. It is the entire margin.

The four line items free calculators drop

The gross-minus-30% shortcut reports $20,992 on this property, a figure 53 times the honest answer. Four omissions produce almost all of it.

Cleaning treated as revenue is the biggest. A calculator that adds $13,135 of cleaning fees to revenue and never subtracts the $12,425 paid to cleaners overstates net by $12,425 on its own. Platform fee modeled at 3% instead of 15.5% adds another $10,264, and the 3% figure is stale for anyone running a PMS.

Lodging tax is the third. Most operators pass it through and Airbnb remits it, in which case it is correctly absent from the model. Anyone absorbing it, or operating direct bookings without automated remittance, is carrying a real cost.

The City of Scottsdale publishes both layers: a 1.7% privilege tax on rental of real property plus a 5.0% transient lodging tax on stays of 29 days or less, so the city alone takes 6.7% before the state and Maricopa County add theirs. On $68,930 of nightly revenue the city portion is $4,618. A model that assumes pass-through and turns out to be wrong loses more than the entire year's cash flow.

Fourth is the reserve. A property with no maintenance or capital line in the model is a property assuming the water heater is immortal. At 6% of net revenue this deal reserves $3,415, which buys one appliance replacement and one repaint. That is thin, and it is still $3,415 more than most calculators subtract.

Where two paths through the same numbers disagree, the disagreement is the finding. MagicBNB's Self-consistency verification runs returns, payback periods, and ROI through multiple solution paths and surfaces where they diverge, so an underwriting model either returns a high-confidence number or tells you which assumption the answer is hanging on.

The two sensitivities that decide whether you sign

Run occupancy down 10% and ADR down 10%, separately and together, before anything else. On this deal the results are decisive.

Occupancy at 55.8% instead of 62% drops NOI to $31,644 and cash flow to negative $4,810. ADR at $274.50 instead of $305 drops NOI to $31,376 and cash flow to negative $5,078. Both at once produces a $9,752 annual loss and a 4.56% cap rate.

Breakeven occupancy on this property is 61.5%. The underwriting assumed 62%.

Half a point of margin between your assumption and your breakeven is not a forecast. It is a coin flip you have already paid $201,800 to enter.

A deal that survives both single-variable shocks with positive cash flow is a deal you can hold through a soft year. A deal that only works at the base case needs either a lower purchase price, a larger down payment, or a market where your ADR assumption is backed by your own booked history rather than a market estimate.

Comparing shocked cases across several candidates is where most operators lose the thread. MagicBNB's Deal Analyzer keeps saved analyses in one repository and scores them against your own risk tolerance and target return, so the fourth property you underwrite is ranked against the first three rather than judged alone.

For the full offer-to-close process around these numbers, see magicbnb.io/blog/how-to-underwrite-short-term-rental. For the formula layer underneath the twelve inputs, see magicbnb.io/blog/airbnb-investment-calculator-formula.

Frequently asked questions

What is a short term rental calculator?

A short term rental calculator is a model that converts purchase price, financing terms, ADR, and occupancy into annual cash flow, cap rate, and cash-on-cash return. Most free versions use six inputs and stop at gross revenue minus a flat expense ratio, which overstated cash flow by $20,595 on the worked example above.

How many inputs do you need to underwrite an Airbnb deal?

Twelve. Purchase price, down payment, interest rate and term, closing costs, furnishing capital, ADR, occupancy, occupancy denominator, cleaning economics, platform fee, lodging tax treatment, and fixed annual carry. Roughly thirty other common fields move the year-one answer by under $500 each.

What is a good cash-on-cash return for a short-term rental?

Most operators underwriting in 2026 target 8% to 12% cash-on-cash in year one, and the worked example above returns 0.20%, which is a decline rather than a marginal buy. Anything under about 5% leaves no room for a soft season, since a 10% occupancy miss on this deal swings the result by roughly $5,200.

Should cleaning fees count as revenue in an STR calculator?

No. Cleaning fees should be modeled as a near-zero pass-through, because the fee collected and the cleaner paid usually land within a few percent of each other. On the example property $13,135 collected against $12,425 paid nets $710 for the year, and counting the gross figure as revenue overstates net income by $12,425.

Do short-term rental calculators account for lodging taxes?

Most do not, and it matters only when you absorb the tax rather than pass it through. Scottsdale's city layer alone is 6.7%, combining a 1.7% privilege tax with a 5.0% transient lodging tax, which is $4,618 on $68,930 of nightly revenue before the state and county portions.

What occupancy rate should I use if the property has no booking history?

Use the occupancy your breakeven math can survive, then check whether the market supports it, rather than the reverse. This property breaks even at 61.5%, so any market estimate below roughly 68% leaves no usable margin, regardless of what a comp set reports.

Run the shocked case before the base case

Underwrite your next deal at 90% of your ADR assumption and 90% of your occupancy assumption first. If the answer is still positive, the base case is a bonus rather than a requirement. Model purchase and lease deals side by side in MagicBNB →

About MagicBNB

MagicBNB is a portfolio intelligence platform for short-term rental operators running 2 to 20 doors. Its 60+ metrics glossary keeps Cap Rate, NOI, DSCR, and Cash-on-Cash Return computed to one consistent definition across every view, its Profitability & P&L gives per-property margin any day of the month rather than at year-end, and its Net Payout source of truth drives a single canonical calculation everywhere, so the return you underwrote reconciles against the deposit that actually cleared. See it at magicbnb.io.