Fidamen

Rental Property Calculator

This calculator provides multiple analysis modes for rental property investments including Net Operating Income (NOI), capitalization rate (cap rate), mortgage payments, annual debt service, cash flow before tax, and cash-on-cash return. Use the mortgage mode to model financed purchases and the cap-rate mode for quick underwriting.

Values are estimates for screening and scenario planning. Always reconcile to official loan documents, local tax statements, insurance quotes, and a qualified accountant or attorney for tax and compliance advice.

Updated Nov 29, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record 2fc5ff82fbc2 • Reviewed by Fidamen Standards Committee

Includes mortgage amortization, annual debt service, cash flow before tax and cash-on-cash return. Default method for financed purchases.

Inputs

Results

Updates as you type

Monthly Mortgage Payment

-$2.50

Annual Debt Service

-$30.00

Net Operating Income (NOI)

$14,880.00

Cash Flow Before Tax (annual)

$14,910.00

Total Cash Invested

$63,000.00

Cash-on-Cash Return

2366.67%

OutputValueUnit
Monthly Mortgage Payment-$2.50USD
Annual Debt Service-$30.00USD
Net Operating Income (NOI)$14,880.00USD
Cash Flow Before Tax (annual)$14,910.00USD
Total Cash Invested$63,000.00USD
Cash-on-Cash Return2366.67%%
Primary result-$2.50

Visualization

Methodology

Calculations follow standard real estate underwriting conventions: annualizing monthly income, subtracting vacancy to obtain effective gross income, and subtracting operating expenses to derive NOI.

Mortgage amortization uses a fixed-rate annuity formula to compute level monthly payments and annual debt service. Cash-on-cash return divides pre-tax annual cash flow by total cash invested (down payment, closing costs, rehab).

For trust and reproducibility, engineering and accuracy practices align with industry good practices and controls recommended by standards bodies. This tool recommends verification of inputs and periodic calibration against actual performance data; see citations for relevant standards and guidance.

F.A.Q.

How accurate are results?

Results are estimates based on the inputs and the formulas shown. Accuracy depends on input quality. This tool does not replace lender underwriting, appraisals, inspections, or tax advice. Validate results against actual loan offers, tax bills, and insurance quotes.

Should I include principal paydown in returns?

This calculator shows pre-tax cash flow and commonly used metrics (NOI, cap rate, cash-on-cash). Principal paydown and tax effects increase total investor return but are excluded from the core cash-on-cash calculation. Use the outputs as building blocks to model total return separately.

Are regulatory or safety standards applied?

This tool references recognized standards and recommends that users follow applicable regulatory, safety, and data-handling guidance (see citations). It does not automate compliance checks for local building, safety, or landlord-tenant laws.

What are typical calibration limits?

Inputs like vacancy rate, management fees, and repair reserves should be based on local market data and historical performance. If inputs are outside reasonable bounds (for example, negative rents or vacancy far above 100 percent), results may be invalid. Use sensitivity testing to understand outcome ranges.

Sources & citations

Further resources

Versioning & Change Control

Audit record (versions, QA runs, reviewer sign-off, and evidence).

Record ID: 2fc5ff82fbc2

What changed (latest)

v1.0.0 • 2025-11-29 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Public QA status

PASS — golden 25 + edge 120

Last run: 2026-01-23 • Run: golden-edge-2026-01-23

Engine

v1.0.0

Data

Baseline (no external datasets)

Content

v1.0.0

UI

v1.0.0

Governance

Last updated: Nov 29, 2025

Reviewed by: Fidamen Standards Committee (Review board)

Credentials: Internal QA

Risk level: low

Reviewer profile (entity)

Fidamen Standards Committee

Review board

Internal QA

Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person

Semantic versioning

  • MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
  • MINOR: New features or fields that do not change existing outputs for the same inputs.
  • PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.

Review protocol

  • Verify formulas and unit definitions against primary standards or datasets.
  • Run golden-case regression suite and edge-case suite.
  • Record reviewer sign-off with credentials and scope.
  • Document assumptions, limitations, and jurisdiction applicability.

Assumptions & limitations

  • Uses exact unit definitions from the Fidamen conversion library.
  • Internal calculations use double precision; display rounding follows the unit's configured decimal places.
  • Not a substitute for calibrated instruments in regulated contexts.
  • Jurisdiction-specific rules may require official guidance.

Change log

v1.0.0 • 2025-11-29 • MINOR

Initial publication and governance baseline.

Why: Published with reviewed formulas, unit definitions, and UX controls.

Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: 634c88ba1b91