Our Methodology & Data Sources
Every number on USFinNexus comes from a verifiable, official government or industry source. Here is exactly how our calculators work and where our data comes from.
Last Updated: May 10, 2026
Calculation Principles
- All formulas use standard US monthly compounding (not annual compounding)
- Loan limit thresholds are updated annually to reflect FHFA and HUD announcements
- Default rate values reflect the current Freddie Mac PMMS weekly average
- Property tax rates use the Tax Foundation effective rate, not statutory rates
- DTI guidelines follow CFPB Qualified Mortgage standards (effective 2021+)
Primary Data Sources
Consumer Financial Protection Bureau (CFPB)
official sourceMortgage payment formulas, Qualified Mortgage DTI guidelines (28% front-end / 43% back-end), ability-to-repay standards, and PMI cancellation rules under the Homeowners Protection Act.
Federal Housing Finance Agency (FHFA)
official source2026 conforming loan limits: $832,750 baseline / $1,249,125 high-cost areas. Used in our mortgage and affordability calculators to flag jumbo loan thresholds.
U.S. Department of Housing and Urban Development (HUD)
official source2026 FHA loan limits: $541,287 floor / $1,249,125 ceiling. FHA mortgage insurance premium (MIP) rates and USDA income guidelines used in our government loan calculator.
Tax Foundation
official sourceState-by-state effective property tax rates used in our mortgage, affordability, and Texas/California/Florida state calculators.
Freddie Mac Primary Mortgage Market Survey
official sourceWeekly average 30-year and 15-year fixed mortgage rates used as default pre-filled values in our calculators to reflect current market conditions.
National Association of Realtors (NAR) / Redfin
official sourceMedian home price data by state used in state-specific calculator defaults and blog post examples.
Core Calculation Formulas
Monthly Mortgage Payment (P&I)
M = P × [r(1+r)ⁿ] / [(1+r)ⁿ - 1]Where M = monthly payment, P = principal loan amount, r = monthly interest rate (annual rate ÷ 12), n = total number of payments (years × 12).
Debt-to-Income Ratio (DTI)
DTI = (Total Monthly Debt Payments ÷ Gross Monthly Income) × 100Front-end DTI includes only PITI (principal, interest, taxes, insurance). Back-end DTI includes all recurring monthly debt obligations per CFPB Qualified Mortgage guidelines.
Loan-to-Value Ratio (LTV)
LTV = (Loan Amount ÷ Appraised Property Value) × 100LTV determines PMI requirement (required if LTV > 80%), eligibility for cash-out refinancing (max 80% LTV for most conventional loans), and jumbo loan classification.
PMI Calculation
Annual PMI = Loan Amount × PMI RatePMI rates range from 0.5%-1.5% of the loan amount annually, varying by credit score, LTV, and loan type. PMI is automatically canceled at 78% LTV per the Homeowners Protection Act of 1998.
Refinance Break-Even
Break-Even Months = Total Closing Costs ÷ Monthly Payment SavingsIf the break-even period is less than your planned remaining stay in the home, refinancing is financially beneficial. Closing costs typically range from 2%-5% of the new loan amount.
Important Limitations
- Calculator results are estimates only and do not constitute financial or mortgage advice.
- Actual loan terms, rates, and qualification depend on your individual creditworthiness and lender policies.
- Property tax rates are effective averages and vary by specific county and municipality.
- Homeowners insurance estimates are national averages; your actual premium depends on location, coverage, and insurer.
- Always consult a licensed mortgage professional or financial advisor before making home purchase decisions.