The exact math and government data behind all 11 tools on this site — VA funding fee tables, residual income thresholds, FHFA loan limits, DoD BAH rates, and standard amortization formulas. No black boxes: here's precisely how every number is produced.
Every payment-based calculator on this site uses the standard amortization formula for a fixed-rate loan. Interest-only, adjustable-rate, and buydown structures are not modeled unless the tool says so.
The math
M = P × r(1 + r)ⁿ ÷ ((1 + r)ⁿ − 1), where M is the monthly payment, P is the loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the number of monthly payments (years × 12).
Used by: Purchase, Refinance, Construction, Affordability, Rent vs Buy
VA Funding Fee
VA Lender's Handbook (Pamphlet 26-7), Chapter 8
The funding fee is calculated as a percentage of the loan amount, using the VA's published fee tables. The percentage depends on loan type (purchase, cash-out refinance, IRRRL), first or subsequent use, down payment tier, and exemption status. Veterans receiving VA disability compensation and eligible surviving spouses are exempt — our tool applies a 0% fee when you indicate an exemption.
The math
Funding fee = loan amount × fee percentage from the current VA table. Example: first-use purchase with less than 5% down uses the base first-use tier. When financed, the fee is added to the loan amount before the payment is calculated.
Used by: Funding Fee calculator, Purchase, Refinance, IRRRL
Residual Income
VA Lender's Handbook (Pamphlet 26-7), Chapter 4
VA underwriting requires a minimum amount of residual income — money left each month after major obligations. The VA publishes minimums by region (Northeast, Midwest, South, West), family size, and loan amount tier. Our calculator subtracts housing expense, debts, and estimated maintenance and utilities from gross income, then compares the result to the VA table for your region and family size.
The math
Residual income = gross monthly income − total housing payment − recurring monthly debts − estimated maintenance & utilities. Result is compared against the Chapter 4 table minimum for your region and family size.
Used by: Residual Income calculator, Affordability
Debt-to-Income (DTI) Ratio
VA Lender's Handbook (Pamphlet 26-7), Chapter 4
DTI is total monthly debt obligations divided by gross monthly income. The VA benchmark is 41%, but the handbook allows higher ratios when residual income exceeds the minimum by a sufficient margin or other compensating factors exist. Our tools show both figures because VA underwriting weighs them together.
The math
DTI = (total monthly housing payment + recurring monthly debts) ÷ gross monthly income. Recurring debts include minimum payments on installment loans, credit cards, and other obligations per the handbook's definitions.
Used by: Affordability, Residual Income calculators
Loan Limit Lookup
FHFA conforming loan limits + U.S. Census ZIP-to-county data
You enter a ZIP code; Census crosswalk data maps it to a county; the tool returns the FHFA conforming limit for that county. VA borrowers with full entitlement have no VA-imposed cap — limits matter for partial entitlement, where the VA guaranty is based on the county limit minus entitlement already in use.
The math
With partial entitlement, maximum VA guaranty = 25% of the county conforming limit − entitlement already charged. The amount you can borrow with no down payment follows from that guaranty, subject to lender approval.
Used by: Loan Limit Lookup, Entitlement calculator
VA Entitlement
VA Lender's Handbook (Pamphlet 26-7), Chapters 2 & 5
Entitlement is the amount the VA guarantees on your loan. Veterans with full entitlement are not subject to county loan limits. Veterans with entitlement tied up in an existing VA loan use the remaining-entitlement calculation to see whether a second VA loan requires a down payment.
The math
Remaining guaranty = 25% of county limit − entitlement in use. If 4 × remaining guaranty is less than the new loan amount, the difference becomes a down payment requirement to satisfy the 25% guaranty rule.
Used by: Entitlement calculator, Loan Limit Lookup
IRRRL & Refinance Breakeven
Standard time-value comparison, VA Pamphlet 26-7 (IRRRL rules)
Refinance tools compare your current payment to the new payment and divide total closing costs by the monthly savings to find the breakeven point. The VA also requires an IRRRL to pass a recoupment test — fees and costs must be recouped within 36 months — which our IRRRL tool applies.
The math
Breakeven (months) = total closing costs ÷ monthly payment savings. IRRRL recoupment: (fees + closing costs, excluding prepaids) ÷ monthly P&I reduction must be ≤ 36 months.
Used by: IRRRL calculator, Refinance calculator
BAH Match
Defense Travel Management Office (DTMO), DoD
BAH Match compares your Basic Allowance for Housing — published annually by the DTMO by ZIP code, pay grade, and dependency status — against an estimated monthly housing payment at your entered price point, rate, and down payment. BAH rates are sourced from the DoD's official tables and refreshed with each annual release.
The math
Estimated payment uses the standard amortization formula above, plus estimates for taxes and insurance where indicated. The tool compares that payment to the BAH rate for the selected ZIP and pay grade.
Used by: BAH Match calculator
Rent vs Buy
Standard comparison modeling with user assumptions
This tool compares the monthly and cumulative cost of renting against owning, using your rent, expected rent growth, home price, rate, and estimated ownership costs. It is a simplification: it does not model home-price appreciation, tax effects, maintenance variance, or opportunity cost unless you enter them.
The math
Cumulative rent = monthly rent grown at your annual rent-increase assumption. Cumulative ownership cost = mortgage payments (amortization formula) + entered taxes, insurance, and costs. The crossover point is where the two totals meet.
Used by: Rent vs Buy calculator
Taxes, Insurance & Closing Cost Estimates
User-entered values and clearly labeled estimates
Property taxes, homeowners insurance, and closing costs vary widely by state, county, and lender. Where our tools include them, they use either your own entered values or labeled placeholder estimates — never invented local data. Final figures always come from your Loan Estimate and closing disclosure.
The math
Where defaults appear, they are conservative planning estimates shown as editable fields, so you can replace them with real quotes for your area.
Used by: Purchase, Affordability, Construction, Rent vs Buy
What These Tools Are — and Aren't
These calculators are educational estimates built on published formulas and government data. They are not loan approvals, rate quotes, pre-qualifications, or commitments to lend. Real underwriting uses your verified income, credit, Certificate of Eligibility, appraisal, and the current official tables — and can produce different results. When the VA, FHFA, or DoD releases new figures, we update the affected tools and note the review date on this page.
Military Mortgage LLC is a mortgage broker and is not affiliated with, endorsed by, or acting on behalf of the U.S. Department of Veterans Affairs, the U.S. Department of Defense, or the FHFA. Official sources are linked on our Data Sources page so you can verify every input yourself.
MilitaryMortgage.com is the official website of Military Mortgage LLC, a mortgage broker. Military Mortgage LLC is not affiliated with, endorsed by, or acting on behalf of the U.S. Department of Veterans Affairs, the U.S. Department of Defense, or any other government agency.
We offer VA, FHA, Conventional, USDA, and Non-QM loan programs. All loans are subject to applicable credit, income, property, program, and underwriting requirements. Rates, terms, programs, and eligibility requirements are subject to change without notice. Equal Housing Opportunity
