About DealMath

DealMath is a free suite of financial calculators for real estate investors. Rentals, BRRRRs, flips, 1031 exchanges, depreciation, syndication waterfalls, DSCR loans — the math that turns a listing into a decision, all in one place.

What we do

We build precise, fast, share-friendly investment math tools. Every calculator is designed to answer one question well, render results instantly, and generate a clean shareable URL so investors can drop a deal into a Slack channel, a Reddit thread, or a partner's inbox without rebuilding the spreadsheet on the other end.

The site is free to use. There is no signup, no paywall, and no email gate.

How the math works

The numbers on this site are computed by a TypeScript math library that is unit-tested against textbook reference cases. The library covers:

• Cash flow underwriting — gross rent, vacancy, operating expenses (taxes, insurance, management, maintenance, CapEx reserves, HOA, utilities), and debt service with monthly amortization.
• Yield metrics — net operating income (NOI), capitalization rate, cash-on-cash return, gross rent multiplier (GRM), and debt yield computed from underwritten cash flow.
• Debt service coverage ratio (DSCR) — NOI ÷ annual debt service, with a solver for the maximum loan or purchase price at a target DSCR.
• Multi-year projections — rent growth, expense inflation, appreciation, and a standard mortgage amortization schedule across the hold period.
• Internal rate of return (IRR) — Newton-Raphson solver over modeled hold-period cash flows including sale at exit (net of selling costs and remaining loan payoff).
• BRRRR cycle — initial capital, hard-money carry, ARV refinance at target LTV, cash recycled vs. cash left in the deal, and stabilized cash flow at the refinance payment.
• Fix-and-flip math — purchase, rehab, holding, and selling costs, gross and net profit, ROI, annualized ROI, and the 70% rule check.
• 1031 exchange — realized gain, recognized gain, cash and mortgage boot, deferred tax, and basis carryover into the replacement property.
• Depreciation — 27.5-year residential and 39-year commercial straight-line schedules, with optional bonus depreciation and an estimated §1250 recapture liability at sale.
• Syndication waterfall — limited-partner / general-partner splits with preferred return, catch-up tier, and promote tiers, distributed year by year.
• Short-term-rental (Airbnb) ROI — occupancy, average daily rate (ADR), cleaning, channel fees, and seasonality applied to a standard rental model.

Test cases for the math library are anchored against published textbook examples and hand-verified scenarios. If you find an output that doesn't match a reputable source, please email support@dealmath.app with the inputs and the expected number — we'll investigate and ship a fix.

What we deliberately do not do

DealMath is a calculation tool. It is not:

• Legal advice. Entity structuring, lease drafting, tenant disputes, and 1031 qualified-intermediary selection should go through a licensed attorney in your jurisdiction.
• Tax advice. Depreciation strategy, cost segregation, recapture planning, and entity-level taxation should go through a licensed CPA who has reviewed your full return.
• Investment advice. We do not recommend specific properties, markets, deals, lenders, partners, or strategies. The output of every calculator is a math result, not a buy or sell signal.
• Real-time market data. We do not source live cap-rate comps, rent comps, property values, mortgage rate quotes, or trading data. Every number you see is computed from the inputs you provide.

Use the calculators to model scenarios and pressure-test assumptions. Make the actual decision with qualified professionals who carry appropriate licensing and insurance.

How we make money

Display advertising and clearly disclosed affiliate links to investor-focused services (property-management software, landlord insurance, lender platforms, accounting tools). Affiliate relationships never influence the math, the rankings, or which tools appear on the site. If we don't use the underlying product ourselves or wouldn't recommend it independently, we don't link to it. See the privacy policy for the full list of advertising and analytics integrations in use.

Contact

Bug reports, math corrections, feature requests, or partnership inquiries: support@dealmath.app.

Disclaimer: The information and tools on DealMath are provided for general informational and educational purposes only and do not constitute legal, tax, accounting, financial, or investment advice. DealMath makes no representations or warranties regarding the accuracy, completeness, or suitability of any output for any particular purpose. You should consult a qualified attorney, certified public accountant, and licensed financial professional before making any investment, tax, or legal decision based on results produced by this site.