Shared conventions
Examples use US dollars. Rates and prices entered by default are illustrative, not live quotes or forecasts. Calculations retain precision internally and round displayed money to cents. The two-room split rounds the first share to cents and allocates the remaining cents to the second so the shares add to the total.
All calculations run in your browser. Saved comparisons exist only in page memory. Results can be downloaded as CSV with inputs and outputs; the download is generated locally.
Income and expense definitions
Personal rent affordability uses take-home pay. Rental-property NOI means effective income after recurring operating expenses, before principal-and-interest debt service, income tax, and the separately entered capital reserve. Cash flow subtracts debt service and that reserve. Lenders and analysts can use other definitions; reconcile them before comparison.
Fixed-rate loans
Mortgage payments assume monthly payments on a fully amortizing fixed-rate loan. Annual note rate is divided by twelve for the monthly rate. At zero interest, principal is divided evenly across payments. Taxes, insurance, HOA, and mortgage-insurance amounts are separate user estimates. The tool does not recalculate or automatically cancel mortgage insurance.
Rent vs. buy wealth comparison
The renter invests the buyer’s down payment plus buying costs at the beginning. Each month, both investment accounts first grow at the monthly equivalent of the selected effective annual return. The household with lower modeled housing costs then invests the difference at month end.
Monthly rent changes at each annual anniversary. Home value changes at the entered annual rate. Owner operating costs remain constant, loan payments end after the selected loan term, and sale equity deducts hypothetical selling costs and outstanding debt. Owner wealth equals sale equity plus invested monthly savings. Renter wealth equals the modeled investment account. Taxes, moving costs, renters insurance, and utility differences are excluded.
Check any individual tool
Each calculator has its own inputs, example, method, and limitations. These formulas describe a planning model rather than a substitute for an actual lease, loan, or professional analysis.
Rent affordability calculator
Rent budget = max(0, min(take-home pay × target share, take-home pay − spending − utilities − savings))The target percentage is your own planning choice. This does not estimate gross income, taxes, eligibility, local housing prices, deposits, or one-off moving costs. A zero result means your chosen commitments leave no room for rent; it is not a statement about housing eligibility.
Rent split calculator
Room share = (rent × shared fraction ÷ 2) + (rent × private fraction × room area ÷ combined room area)This model supports exactly two rooms with one payer per room. It does not price private bathrooms, couples sharing a room, parking, natural light, or noise. Agree any extra adjustments separately. It does not alter liability under a lease.
Prorated rent calculator
Prorated rent = monthly rent ÷ days in month × billable days (calendar method)The calculator does not decide whether rent must be prorated. It excludes deposits, utilities, concessions, and fees. Your lease and applicable rules control billing. A 30-day method can exceed a full month of rent for 31 billed days unless the contract caps the charge.
Rent increase calculator
Change (%) = (proposed rent − current rent) ÷ current rent × 100This tool measures a change; it does not determine whether it is permitted. Notice requirements, regulated rents, lease terms, concessions, and local exemptions must be checked separately. Negative changes are supported and represent a rent reduction.
Mortgage payment calculator
P&I = L × r ÷ (1 − (1 + r)^−n), where L is loan balance, r monthly interest, and n monthly paymentsAssumes a fully amortizing fixed-rate loan with monthly payments and no extra principal. Excludes closing costs, maintenance, utilities, points, and rate changes. Tax and insurance amounts remain constant in this model; actual bills can change.
Rent vs. buy calculator
Owner wealth = sale value − selling costs − remaining loan + invested monthly savings; renter wealth = invested upfront cash + invested monthly savingsA simplified nominal, pre-tax scenario. It excludes income-tax deductions, capital-gains taxes, renters insurance, deposit opportunity cost, utilities, moving costs, and variable-rate loans. Annual property bills and HOA stay flat. Entered mortgage insurance stays constant until the scheduled loan term ends; early cancellation is not modeled. Rent and property value change at your chosen rates. It assumes all monthly savings are invested. Its final-period advantage is not a guarantee or a permanent break-even claim.
Down payment savings calculator
Months = ceiling(max(0, price × (down payment % + buying cost %) + reserve − savings) ÷ monthly contribution)This is a savings timeline, not a statement of loan eligibility or required down payment. It assumes no investment return, price inflation, changing income, withdrawals, or assistance programs. Revisit your price and closing-cost inputs as your search develops.
Closing cost calculator
Cash to close = down payment + closing allowance + separate prepaids − deposit − eligible creditsActual fees depend on location, loan, transaction terms, and timing. This does not calculate program-specific credit limits, transfer taxes, rate-lock fees, discount points, or financed charges. A Closing Disclosure controls the final transaction figures. Deposits are not a second cost; they reduce cash remaining.
Rental cash flow calculator
Monthly cash flow = rent × (1 − vacancy %) + other income − operating costs − debt service − capital reserveA steady-state, pre-tax estimate. Vacancy applies to base rent only; other income is assumed collectible. Reserves are planned allocations rather than a prediction of when repairs will occur. Excludes appreciation, sale costs, income tax, depreciation, and loan principal as a separate return component.
Cap rate calculator
Cap rate = annual NOI ÷ property value × 100; implied value = annual NOI ÷ target cap-rate fractionCap rate excludes financing, acquisition costs, capital reserves, income taxes, and appreciation. It is a one-year income snapshot. Negative NOI produces a negative cap rate and no meaningful positive income-capitalization valuation. A higher cap rate can signal higher risk, not simply a better purchase.
Cash-on-cash return calculator
Cash-on-cash return = annual pre-tax cash flow ÷ total upfront cash committed × 100Excludes appreciation, loan principal reduction, income taxes, sale proceeds, and timing within the year. It is not IRR or total ROI. Different analysts handle reserves differently; this page includes initial funded reserves in invested cash. A zero cash denominator is undefined.
DSCR calculator
DSCR = annual NOI ÷ annual debt service; debt capacity at target = annual NOI ÷ target DSCRLenders may use adjusted NOI, include reserves, or use rent divided by PITIA for certain residential products. This tool uses only NOI divided by principal-and-interest debt service. It does not establish loan eligibility, loan size, or approval. Target capacity is shown as zero when NOI is not positive.
Net effective rent calculator
Net-effective base rent = (gross monthly rent × lease months − free-month rent − additional rent credit) ÷ lease monthsAssumes constant gross rent and entered costs for the whole lease. It does not decide concession eligibility, repayment/clawback terms, renewal rent, local fee legality, credit timing, or the cash deposit required. Utilities are your estimates. The all-in average includes only the categories you supplied.
Extra mortgage payment calculator
Monthly interest = outstanding balance × annual rate ÷ 12; new balance = old balance + interest − scheduled payment − extra principalAssumes a fully amortizing fixed-rate loan, monthly interest, no fees, no payment deferrals, and extra principal applied with every payment from next month. The calculated scheduled payment may differ from an actual statement with a nonstandard remaining term or rounding. Excludes taxes, insurance, PMI, recasting, refinancing, opportunity cost, and prepayment penalties. Check your contract and servicer instructions.
Rental property expense calculator
NOI = effective income − taxes − insurance − management − routine repairs − HOA − owner utilities − other operating costs; cash flow = NOI − debt service − capital reserveA pre-tax steady-state worksheet, not a forecast or tax deduction schedule. Other income is assumed collectible and is not reduced by the base-rent vacancy allowance. Management contracts can use a different fee base or fixed minimum. Excludes appreciation, sale costs, depreciation, tenant-specific information, and an inspection-based replacement schedule. The stress table changes vacancy only; it does not model all downside risks.
Checks and corrections
The source includes numerical tests for representative examples, zero-interest mortgages, loan repayment, exact rent allocation, credits, negative returns, and rent-vs-buy investment flows. Passing those checks supports the implementation; it does not prove that a scenario matches a particular transaction.
If you find a difference, send a reproducible report with non-sensitive example inputs. We will compare the arithmetic and definitions before deciding how the tool or explanation should change.