How does BNBCalc estimate operating expenses?

How BNBCalc adds up operating expenses

Operating expenses are the costs of running the rental before any mortgage. BNBCalc sorts them into three groups and adds them up each month:

• Utilities = internet and TV + water and sewer + garbage + electric + gas + other utilities
• Maintenance = insurance + HOA + landscaping + repairs + supplies + property software + pest control + permits + other + cleaning, where cleaning = monthly revenue × cleaning %
• Management = monthly revenue × (host platform fee % + property management fee % + lodging tax %)

Operating expenses = utilities + maintenance + management

Revenue minus those expenses is operating income, BNBCalc's version of net operating income (NOI). Property tax and mortgage insurance aren't in the list, because BNBCalc keeps them with the loan payment under Mortgage & Taxes. That matters when you compare its cap rate with another calculator's.

The starting values

A new analysis of a US property, or one in another high-income country, starts with these defaults:

Properties in lower-income countries start with lower defaults. If you've saved a default preset, your own numbers replace these, and anything you type into an analysis overrides both.

The platform fee default follows Airbnb's single host fee, which BNBCalc assumes is 15.5%, or 16% for listings in Brazil and Mexico. If you also take Vrbo or direct bookings, you'll want to enter a blended rate across your channels instead. For cleaning, typing a dollar amount rewrites the percentage to match, so you can work in whichever you know.

A worked example

Take the same three-bedroom home from How does BNBCalc estimate revenue for a property?. After your first change in the revenue section, it's estimated at $60,000 a year, or $5,000 a month. With every expense default left in place, the illustrative numbers look like this:

Over a full year, those expenses come to $27,780, which leaves $32,220 of operating income before the mortgage. How does BNBCalc calculate cash flow and returns? picks the example up from there.

Letting AI estimate the expenses

The defaults don't know anything about the specific home, so a four-bedroom with a pool starts with the same water bill as a city condo. To tailor them, click Estimate with AI next to the Profit heading. It works if you're signed in and on a paid plan, or have a free analysis left.

BNBCalc then proposes a value for each field it can estimate, with the reason, the source and a confidence level, and you tick the ones you want and click Apply selected. The estimates come together in this order:

1. Fixed rules scale the defaults to the property's size and features, such as bedrooms, bathrooms, square feet, a pool or a hot tub.
2. Facts from the property's listing record, like HOA dues, property insurance and property tax, come next.
3. Where at least 10 nearby listings publish a cleaning fee, the market's cleaning-fee data sets the cleaning percentage.
4. AI fills in whatever's left, within limits: property tax no higher than 3% of the price a year, and cleaning between 3% and 25% of revenue.

It never changes the Airbnb Fee, Property Management Fee, Lodging Tax, mortgage insurance, Permits, Other, Property Software, or Rental Insurance on Rent analyses. If a field's current value came from one of your saved presets, its proposal starts unticked, so you won't overwrite your own numbers by accident. AI estimates also don't run on their own when an analysis is created.

Saving your own numbers as presets

If you use the same cleaner, manager or insurance quote on every deal, save those numbers as a preset: a named set of values you can apply to any analysis. Mark one as your default and every new analysis starts from it instead of BNBCalc's defaults. How do I add or edit expenses? shows where to find it.

One last thing to keep in mind: analyses created before October 2026 keep the defaults they started with, most recently 10% cleaning and a 3% platform fee. Only new analyses pick up the current ones.