Rental Income Calculator
This multi-method rental income calculator estimates Net Operating Income (NOI), capitalization rate, cash-on-cash return, and an illustrative after-tax cash flow. It is intended for planning and comparison of rental investments.
Results are based on user-provided inputs and standard financial formulas. Use values that match your local market and consult professionals for underwriting, tax, and legal advice.
Governance
Record 3d0b9634e1c3 • Reviewed by Fidamen Standards Committee
Compute effective gross income, operating expenses, Net Operating Income (NOI), annual mortgage payments and net annual cash flow.
Inputs
Results
Net Operating Income (NOI)
$11,400.00
Annual mortgage payment
-$30.00
Annual cash flow (before tax)
$11,430.00
| Output | Value | Unit |
|---|---|---|
| Net Operating Income (NOI) | $11,400.00 | USD |
| Annual mortgage payment | -$30.00 | USD |
| Annual cash flow (before tax) | $11,430.00 | USD |
Visualization
Methodology
Calculations follow common real-estate finance conventions: gross rent less vacancy yields effective gross income; NOI equals effective gross income minus recurring operating expenses; cap rate is NOI divided by purchase price; cash-on-cash compares pre-tax cash flow to initial cash invested.
Mortgage payments use the standard fixed-rate annuity formula for level payments. Tax estimates are intentionally simplified: they do not replace tax professional calculations and use the marginal tax rate provided by the user.
Key takeaways
Use NOI and cap rate to compare asset value and market yields.
Use cash-on-cash to evaluate short-term liquidity returns on invested equity.
After-tax estimates are illustrative only; they rely on simplified assumptions about interest and depreciation.
Worked examples
Example: $2,000 monthly rent, $0 other income, 5% vacancy, $5,000 operating expenses, $240,000 loan at 4.5% → NOI and annual cash flow are computed to assess both cap rate and cash-on-cash return.
Example: When loan_amount = 0 (cash purchase), annual mortgage payment is treated as zero and cash-on-cash is annual cash flow divided by cash invested.
F.A.Q.
Is this calculator a substitute for professional underwriting?
No. This tool provides illustrative estimates. Use it for initial screening. For financing, tax, or legal decisions, consult a licensed professional and request full amortization schedules and tax computation.
How accurate are mortgage payment calculations?
Mortgage payments are calculated with the standard fixed-rate annuity formula. Rounding and input precision affect cents-level accuracy; amortization schedules and escrow payments are not included.
How does the tool handle taxes?
Tax computations are simplified and illustrative. The tool applies a user-provided marginal tax rate to a simplified taxable income estimate. It does not account for itemized deductions, passive activity loss rules, local taxes, or tax credits.
What if I enter zero or missing values?
Zero loan amount is treated as an all-cash purchase and sets mortgage payments to zero. Missing fields should be completed to obtain meaningful results. Division-by-zero safeguards return zero where appropriate.
Sources & citations
- National Institute of Standards and Technology (data integrity & best practices) — https://www.nist.gov
- International Organization for Standardization (numeric and documentation standards) — https://www.iso.org
- IEEE (engineering and numeric computation best practices) — https://www.ieee.org
- Occupational Safety and Health Administration (OSHA) — guidance for safe workplace practices — https://www.osha.gov
- HUD — FHA Single Family Housing Policy Handbook 4000.1 — https://www.hud.gov/program_offices/housing/sfh/handbook_4000-1
- HUD — Property Valuation and Appraisals (HUD 4155.2) — https://www.hud.gov/sites/documents/4155-2_4.pdf
- Fannie Mae — Selling Guide — https://selling-guide.fanniemae.com/
Further resources
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
Record ID: 3d0b9634e1c3What changed (latest)
v1.0.0 • 2025-11-02 • 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
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
What changed (latest)
v1.0.0 • 2025-11-02 • 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 2, 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 • 2025-11-02 • 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: 4602dc7f8c02