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Mortgages
Understanding Mortgage Affordability: The Complete 2025 Guide
Learn how lenders calculate mortgage affordability, what DTI ratios mean, and how to maximize your buying power with our comprehensive guide to mortgage qualification.
By CalcDomain Team • January 15, 2025 • 12 min read
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Formula (LaTeX) + variables + units
This section shows the formulas used by the calculator engine, plus variable definitions and units.
Note: This page needs review to confirm formulas and sources.
Note: This page needs review to confirm formulas and sources.
No formulas provided in audit spec.
Variables and units
- P = principal (loan amount) (currency)
- r = periodic interest rate (annual rate ÷ payments per year) (1)
- n = total number of payments (years × payments per year) (count)
- M = periodic payment for principal + interest (currency)
- T = property tax (annual or monthly depending on input) (currency)
- I = homeowners insurance (annual or monthly depending on input) (currency)
Sources (authoritative):
- Visit IRS.gov → — irs.gov · Accessed 2026-01-19
https://www.irs.gov/ - Visit CFPB.gov → — consumerfinance.gov · Accessed 2026-01-19
https://www.consumerfinance.gov/ - Visit HUD.gov → — hud.gov · Accessed 2026-01-19
https://www.hud.gov/ - Visit FederalReserve.gov → — federalreserve.gov · Accessed 2026-01-19
https://www.federalreserve.gov/ - Visit VA.gov → — va.gov · Accessed 2026-01-19
https://www.va.gov/ - Visit SSA.gov → — ssa.gov · Accessed 2026-01-19
https://www.ssa.gov/ - Get Free Report → — annualcreditreport.com · Accessed 2026-01-19
https://www.annualcreditreport.com/ - Visit Fannie Mae → — fanniemae.com · Accessed 2026-01-19
https://www.fanniemae.com/
Changelog
Version: 0.1.0-draft
Last code update: 2026-01-19
Last code update: 2026-01-19
0.1.0-draft · 2026-01-19
- Initial audit spec draft generated from HTML extraction (review required).
- Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
- Confirm sources are authoritative and relevant to the calculator methodology.
Verification pending · Last code update: 2026-01-19