Methodology and Sources

Calculator Formulas

Each calculator uses standard financial formulas. Here is how we calculate the key figures:

• Mortgage Payment Calculator

  M = P · [r(1 + r)ⁿ / ((1 + r)ⁿ − 1)] where M = monthly payment, P = principal, r = monthly interest rate (annual rate / 12), n = total number of payments. Supports loan terms from 10 to 30 years.

• Property Tax Calculator

  Annual Property Tax = (Property Value × Assessment Rate) × (Millage Rate / 100); Monthly = Annual / 12. Assessment rates vary by state (10-100% of market value). Millage rates vary by jurisdiction (typically $5-$20 per $1,000 of assessed value).

• Refinance Savings Calculator

  Calculate monthly P&I with current loan; calculate new P&I with refinance terms; compare total interest paid over remaining life. Break-even point = (Closing Costs) / (Monthly Savings). Assess if refinance pays off before selling or moving.

• Mortgage Interest Deduction Calculator

  For mortgages on homes purchased after Dec 15, 2017: Maximum deductible = interest on first $750,000 of debt ($375,000 if married filing separately). Calculate: (Total Interest Paid) × (Qualified Loan Amount / Total Loan Amount). Requires itemizing deductions on Schedule A (Form 1040).

• PMI Calculator

  Annual PMI Premium = Loan Amount × PMI Rate (varies by credit score). Monthly PMI = Annual Premium / 12. PMI rates: 620-639 credit score (1.50%), 640-659 (1.31%), 660-679 (1.23%), 680-699 (0.98%), 700-719 (0.79%), 740-759 (0.58%), 760+ (0.46%) as percentage of original loan amount.

• Affordability Calculator

  Debt-to-Income (DTI) = (Total Monthly Debt Payments / Gross Monthly Income) × 100. Front-end ratio (housing costs) typically capped at 28% of income; Back-end ratio (all debt) typically capped at 36-43% of income. Maximum Affordable Home = (Gross Monthly Income × Acceptable DTI% - Other Monthly Debts) / Monthly Rate Factor.

• Extra Payments Calculator

  Recalculate amortization schedule with additional payments applied to principal. Track faster principal paydown and monthly/yearly interest savings. New Payoff Time = month when balance reaches zero with extra payments; Interest Savings = (Original Total Interest) - (New Total Interest).

• Closing Costs Calculator

  Sum of: Lender Fees (origination, application, processing, credit report) + Settlement Fees (title insurance, appraisal, survey, attorney) + Third-party Fees (inspection, HOA, recording) + Prepaid Expenses (taxes, insurance, prepaid interest, HOA) + Government Fees (transfer tax, recording). Typical total = 2-5% of loan amount.

• Escrow Calculator

  Monthly Escrow = (Annual Property Taxes + Annual Insurance + Annual HOA + Annual PMI) / 12. Lender estimates each component separately and deposits funds in escrow account, paying out annually or semi-annually. Escrow review conducted annually to adjust for changes.

• Rent vs Buy Calculator

  Total Buy Cost = Down Payment + Closing Costs + (Monthly P&I + Taxes + Insurance + HOA + Maintenance) × Months + Selling Costs - Equity Accumulated - Home Value Appreciation. Total Rent Cost = Deposit + (Monthly Rent + Renter's Insurance) × Months + Rent Increases. Break-even point when cumulative buy cost equals cumulative rent cost.

Tax Rules & Sources

Our tax-related figures are based on current IRS publications and federal legislation. We update these rules annually.

• SALT Cap (State and Local Tax Deduction) (2024)

  $10,000 cap ($5,000 if married filing separately). Applies to aggregate of income taxes, sales taxes, and property taxes.

  Source: IRC §164(b); Tax Cuts and Jobs Act of 2017; IRS Publication 17 2024
• SALT Cap (State and Local Tax Deduction) (2025)

  $40,000 cap ($20,000 if married filing separately) for most deductions and business property taxes. Phases down by 30% of MAGI over $500,000 ($250,000 for MFS) to floor of $10,000 ($5,000 for MFS).

  Source: One Big Beautiful Bill (P.L. 119-21); IRS Newsroom IR-2025-103; IRC §164(b)
• SALT Cap (State and Local Tax Deduction) (2026)

  $40,400 cap ($20,200 if married filing separately). Phases down by 30% of MAGI over $505,000 ($252,500 for MFS) to floor of $10,000 ($5,000 for MFS). Increases 1% annually through 2029, then reverts to $10,000 in 2030.

  Source: IRS Newsroom IR-2025-103; Form 1040-ES 2026; One Big Beautiful Bill; IRC §164(b)
• Mortgage Interest Deduction - Debt Limit (2024)

  $750,000 maximum mortgage debt on which interest is deductible ($375,000 if married filing separately). Applies to mortgages on homes acquired after December 15, 2017. Mortgages acquired before that date can use the $1,000,000 limit.

  Source: IRS Publication 936; IRC §163(h); Tax Cuts and Jobs Act of 2017
• Mortgage Interest Deduction - Debt Limit (2025)

  $750,000 maximum mortgage debt on which interest is deductible ($375,000 if married filing separately). Limit is now permanent under One Big Beautiful Bill. Applies to first and second homes combined.

  Source: IRS Publication 936; One Big Beautiful Bill (P.L. 119-21); IRC §163(h)
• Mortgage Interest Deduction - Debt Limit (2026)

  $750,000 maximum mortgage debt on which interest is deductible ($375,000 if married filing separately). Permanently fixed. Applies to acquisition debt on primary and secondary homes.

  Source: IRS Publication 936; One Big Beautiful Bill; IRC §163(h)
• Standard Deduction - Single Filer (2024)

  $14,600 standard deduction for single taxpayers under 65 years old.

  Source: IRS Newsroom; Form 1040-C 2024; IRS Publication 17 2024
• Standard Deduction - Married Filing Jointly (2024)

  $29,200 standard deduction for married filing jointly taxpayers (both under 65 years old).

  Source: IRS Newsroom; Form 1040-C 2024; IRS Publication 17 2024
• Standard Deduction - Single Filer (2025)

  $15,750 standard deduction for single taxpayers under 65 years old. Adjusted for inflation.

  Source: IRS Newsroom IR-2025-103; One Big Beautiful Bill; IRS Publication 17 2025
• Standard Deduction - Married Filing Jointly (2025)

  $31,500 standard deduction for married filing jointly taxpayers (both under 65 years old). Adjusted for inflation.

  Source: IRS Newsroom IR-2025-103; One Big Beautiful Bill; IRS Publication 17 2025
• Standard Deduction - Single Filer (2026)

  $16,100 standard deduction for single taxpayers under 65 years old. Adjusted for inflation.

  Source: IRS Newsroom IR-2025-103; Form 1040-ES 2026; IRS Publication 17 2026
• Standard Deduction - Married Filing Jointly (2026)

  $32,200 standard deduction for married filing jointly taxpayers (both under 65 years old). Adjusted for inflation.

  Source: IRS Newsroom IR-2025-103; Form 1040-ES 2026; IRS Publication 17 2026
• PMI Deduction - Expired Period (2024)

  EXPIRED - No deduction allowed for PMI premiums in 2024. The deduction expired at the end of 2021 and was not available 2022-2024.

  Source: IRC §163(h)(3)(E); provision expired December 31, 2021
• PMI Deduction - Expired Period (2025)

  EXPIRED - No deduction allowed for PMI premiums in 2025. The deduction remained expired following 2021 expiration.

  Source: IRC §163(h)(3)(E); provision expired December 31, 2021
• PMI Deduction - Permanent Reinstatement (2026)

  PERMANENT - Deduction for qualified mortgage insurance premiums permanently allowed starting January 1, 2026. No income phase-out limits. Applies to mortgage insurance contracts issued after December 31, 2006 on acquisition debt for first or second home.

  Source: One Big Beautiful Bill (P.L. 119-21); IRS Publication 505 2026; IRC §163(h)(3)(E)
• PMI Deduction - Allocation Rule (2026)

  Prepaid mortgage insurance premiums allocated ratably over the shorter of: (i) stated term of the mortgage or (ii) 84 months. Treated as qualified residence interest, not separately itemized.

  Source: 26 CFR §1.163-11; IRS Publication 505 2026; One Big Beautiful Bill
• Home Office Deduction - Simplified Method (2024)

  $5 per square foot (up to 300 square feet) simplified method available. Actual expense method also available for mortgage interest and property tax deductions on dedicated home office space.

  Source: IRS Publication 587; IRC §280A
• Home Office Deduction - Simplified Method (2025)

  $5 per square foot (up to 300 square feet) simplified method available. Actual expense method also available for mortgage interest and property tax deductions on dedicated home office space.

  Source: IRS Publication 587; IRC §280A
• Home Office Deduction - Simplified Method (2026)

  $5 per square foot (up to 300 square feet) simplified method available. Actual expense method also available for mortgage interest and property tax deductions on dedicated home office space.

  Source: IRS Publication 587; IRC §280A
• Energy Efficiency Credits - Home Improvements (2024)

  30% credit (up to $3,200 annually for energy-efficient HVAC, windows, doors, insulation, heat pumps; up to $2,000 for heat pump water heaters; up to $1,200 for heat pump clothes dryers). Through 2032.

  Source: IRC §30C; Inflation Reduction Act; IRS Form 5695
• Energy Efficiency Credits - Home Improvements (2025)

  30% credit with adjusted caps for specific improvements. Continues through 2032. Limitations apply based on equipment type.

  Source: IRC §30C; Inflation Reduction Act; IRS Form 5695
• Energy Efficiency Credits - Home Improvements (2026)

  30% credit continues with 2026-specific limitations and caps. Program runs through 2032.

  Source: IRC §30C; Inflation Reduction Act; IRS Form 5695
• Homestead Property Tax Exemption (2024)

  Available in 40+ states and D.C. (state-specific): Reduces assessed property tax value by $5,000 to $50,000+ per state. Typically requires owner-occupancy of primary residence. Some states offer enhanced exemptions for seniors, veterans, or disabled homeowners.

  Source: State property tax statutes vary; National Association of Homebuilders (NAHB) compilation
• Homestead Property Tax Exemption (2025)

  Available in 40+ states and D.C. (state-specific): Reduces assessed property tax value by $5,000 to $50,000+ per state. Typically requires owner-occupancy of primary residence. Many states adjust exemption amounts annually for inflation.

  Source: State property tax statutes vary; National Association of Homebuilders (NAHB) compilation
• Homestead Property Tax Exemption (2026)

  Available in 40+ states and D.C. (state-specific): Reduces assessed property tax value by $5,000 to $50,000+ per state. Typically requires owner-occupancy of primary residence and timely filing with local assessor.

  Source: State property tax statutes vary; National Association of Homebuilders (NAHB) compilation
• Home Sale Exclusion - Capital Gains (2024)

  Exclude up to $250,000 in capital gains ($500,000 if married filing jointly) if owned and lived in home 2 of last 5 years. Can use exclusion once every 2 years.

  Source: IRC §121; IRS Publication 523; Tax Cuts and Jobs Act
• Home Sale Exclusion - Capital Gains (2025)

  Exclude up to $250,000 in capital gains ($500,000 if married filing jointly) if owned and lived in home 2 of last 5 years. Can use exclusion once every 2 years.

  Source: IRC §121; IRS Publication 523; Tax Cuts and Jobs Act
• Home Sale Exclusion - Capital Gains (2026)

  Exclude up to $250,000 in capital gains ($500,000 if married filing jointly) if owned and lived in home 2 of last 5 years. Can use exclusion once every 2 years.

  Source: IRC §121; IRS Publication 523; Tax Cuts and Jobs Act

Property Tax Data

State property tax rates are effective averages based on median home values and reported tax bills. Local rates vary by county and municipality, so these are estimates for planning purposes, not parcel-level accuracy.