Mortgage Affordability Calculator

A couple walks into a lender's office with a combined $145,000 salary. The lender approves them for a $535,000 house. They do the math at home that night: the payment works out to $4,100 including taxes and insurance, which is 47% of their take-home. They walk away. That exact sequence — "approved for way more than we can actually live with" — is one of the oldest threads on r/personalfinance and r/FirstTimeHomeBuyer. This calculator is built for the math they wanted before they sat in the office.

Everything stays in your browser. Your income, your debts, your ZIP, your family size — no server sees any of it, no lender buys the lead, no email capture. There's no signup. There's no "get pre-qualified in 60 seconds" modal. The math is the whole product.

Six things set this apart from the affordability calculators on Bankrate, Zillow, NerdWallet, Rocket Mortgage, or Dave Ramsey's site. First, three ceilings side by side — "what a lender will approve," "a conservative 28/36 budget," and "what you can actually live with after everything else." Most calculators give you one number, and it's almost always the lender-max number, which is what got the couple above into trouble. Second, a loan-type selector that actually changes the math — conventional uses 28/36 from the Fannie Mae Selling Guide, FHA uses 31/43 from HUD Handbook 4000.1, VA uses 41% plus the residual-income overlay from the VA Lenders Handbook Chapter 4. Each answer is different, and that difference matters. Third, VA residual income is a first-class output with the regional threshold by family size — Northeast, Midwest, South, West — surfaced next to your computed residual and a pass/fail flag. The residual test is the actual VA approval gate, and mainstream calculators skip it entirely. Fourth, a self-employed income mode that swaps the input from annual gross to two-year Schedule C net, because lenders qualify 1099 borrowers on Line 31 net income, not gross revenue, and the delta is often 30 to 50 percent. Fifth, a student-loan rule selector that reflects 2026 post-OBBBA reality — Fannie Mae counts the actual IBR payment (as low as $0), FHA counts 0.5% of balance when the reported payment is $0, VA counts the residual-income-backed actual payment. The rule you're qualified under can swing the house price by $90,000. Sixth, a comfort ceiling that subtracts your real monthly expenses from your real take-home and tells you what's actually left for a mortgage. That's the number you live with for 30 years.

Things this tool won't do. It won't pre-qualify you — that requires a credit pull and a lender who will underwrite your specific file. It doesn't fetch live rates; you type the rate your lender quoted or use a sensible current-market placeholder. It doesn't model USDA rural loans, jumbo loans above the $806,500 conforming baseline, or non-QM specialty products. It doesn't pull your credit score from anywhere. What it does is show you, honestly, what the math looks like across the three ceilings you actually need, so when you walk into the lender's office, you already know which ceiling your life fits inside.

Affordability math is a stack of constraints, and which one binds you depends on which loan type and which persona you're using. This section walks through the math each ceiling uses, with citations to the underwriting handbooks where the rules live.

The 28/36 rule and what "front-end" vs "back-end" DTI mean. Lenders care about two ratios. Front-end DTI (also called "housing ratio") is your total monthly housing cost divided by gross monthly income — principal, interest, property tax, homeowners insurance, PMI or MIP, and HOA. Back-end DTI is all recurring debt payments (the full housing cost plus car loans, student loans, credit-card minimums, alimony, child support) divided by gross monthly income. Conventional underwriting under Fannie Mae's Selling Guide B3-6-02 uses 28% front-end and 36% back-end as the guideline, though AUS approvals with strong compensating factors (high credit score, significant reserves) can push the back-end up to 50%. The 28 number is the "housing alone" gate; the 36 number is the "total debt" gate. Whichever binds first is your lender max.

FHA DTI. HUD's FHA Handbook 4000.1 allows 31% front-end and 43% back-end as the guideline, with AUS approval pushing to 46.9%/56.9% when compensating factors are strong. FHA is not automatically "more house" than conventional — the DTI caps are higher but FHA loans carry mortgage insurance premium (MIP) that conventional loans don't. On a loan originated after June 2013, FHA MIP never drops off for the life of the loan unless you refinance into a conventional loan. That 0.55% annual MIP on a $300,000 loan adds $137/month forever, which is why FHA is usually better for the first five to ten years (when you're building equity) and worse over the long run (when conventional PMI would have dropped off at 78% loan-to-value).

VA DTI and the residual income test. The VA doesn't hard-cap DTI. The VA Lenders Handbook Chapter 4 treats 41% back-end as the threshold above which the file needs stronger compensating factors, but the actual approval gate is residual income — cash left in your pocket after all debts are paid. The minimum threshold depends on VA region and family size. For example, the Northeast region requires $450 residual for a household of 1, $1,025 for a household of 4, and an additional $80 per person above 5. The West region is higher; Midwest and South are slightly lower. When your DTI crosses 41%, the VA expects a 20% cushion over the base threshold — so a family of 4 in the Northeast with a 42% DTI needs $1,230 residual, not $1,025. This calculator surfaces the threshold by region + family size and computes your residual from the inputs. No mainstream affordability calculator does this, and it's the single biggest differentiator for VA loan users.

The conservative 25% ceiling. Dave Ramsey's cap is 25% of take-home for housing, on a 15-year fixed mortgage with 20% down. This calculator applies the 25%-of-net rule but isn't dogmatic about the 15-year / 20%-down part — those are separate opinions about risk tolerance, and you can set them yourself. The conservative ceiling takes the stricter of 25% of net take-home or 28% of gross, which produces a number lenders will never advertise because it's smaller than their max. That's the point. If your lender approves $500,000 but your 25%-of-take-home ceiling is $360,000, you live with the $360,000 number, not the $500,000 number.

Self-employed income qualifying. When you toggle the self-employed mode, the income input changes from "annual gross salary" to "two-year average net income from Schedule C line 31 (or K-1 for S-corp owners)." Lenders qualify 1099 borrowers on net taxable income averaged over the most recent two filed tax returns, per Fannie Mae Selling Guide B3-3.2-02. Every deduction you take reduces qualifying income dollar for dollar. A consultant grossing $180,000 who deducts $110,000 in home-office, vehicle, equipment, health insurance, and retirement contributions qualifies on $70,000 of income — not $180,000. Mainstream calculators assume W-2, which silently tells 1099 borrowers they can afford 30 to 50 percent more house than their tax returns actually support. The first conversation with a mortgage underwriter is usually a painful surprise. This tool surfaces the truth upfront.

Student-loan DTI treatment. Three rules are in common use as of May 2026:

- Actual payment. The credit-reported monthly payment, which for federal IBR / PAYE / SAVE borrowers can be as low as $0. Fannie Mae and VA default to this rule per Fannie Mae Selling Guide and VA Lenders Handbook. If you're on a $180/month IBR plan with a $60,000 balance, your DTI counts $180, not the standard $600+ amortized payment.
- 0.5% of balance. When the credit report shows $0 or "deferred" on a student loan, FHA's rule under Handbook 4000.1 II.A.4 is to assume 0.5% of the outstanding balance as the monthly payment. A $60,000 balance counts as a $300/month payment for DTI, regardless of your actual IBR status.
- Standard amortized. A 10-year standard-amortization payment on the outstanding balance at the weighted average interest rate. Some pre-OBBBA lenders used this as a conservative fallback; it also applies when a borrower cannot document their IBR status.

OBBBA (the One Big Beautiful Bill Act) is phasing changes to federal student loan plans through July 2026 and beyond. The practical effect: some borrowers on SAVE, REPAYE, or pre-OBBBA IBR plans are being moved to higher-payment standard or new income-driven plans, which raises their reported monthly payment and therefore their mortgage DTI. The student-loan rule selector in this tool auto-defaults by loan type (Conventional → actual IBR, FHA → 0.5% of balance, VA → actual IBR), but you can override it if your lender tells you something different. A dated note under the selector reminds you the rules are in motion.

Combined-household math. When you add a co-borrower, incomes and debts are summed, but lenders qualify the pair on the lower credit score of the two applicants. The lower credit score also drives the rate — so a couple where one partner has a 740 score and the other has a 660 score prices on the 660. If the 660 score is bringing the file below a rate-tier cutoff, consider applying in one name only, provided the higher-scoring person's income alone is enough to qualify.

Property tax, insurance, and PMI/MIP folded in. All three ceilings use PITI (or PITIA when you add HOA), not bare P&I. Property tax is estimated as a percentage of home value (defaults to 1.10% as a reasonable US average; New Jersey is closer to 2.5%, Hawaii closer to 0.28% — replace with your county's actual rate for accuracy). Homeowners insurance defaults to 0.50% of home value annually, higher in Florida, California, and other high-risk zones. Mortgage insurance is 0.5% annual for conventional loans with less than 20% down (until 78% LTV), 0.55% annual for FHA (for life of loan on post-2013 originations), zero for VA (which has a separate upfront funding fee, rolled into the loan balance rather than paid monthly).

What the math doesn't cover. The tool doesn't model lender overlays (individual lenders often tighten Fannie/FHA/VA rules). It doesn't model doc-type lending (bank-statement loans, DSCR investor loans, asset-depletion loans — each has its own rules). It doesn't apply county-by-county jumbo limits; loans above the current $806,500 conforming baseline have their own pricing and underwriting. It doesn't count non-traditional credit. For any of those, ask your lender directly.

The affordability-calculator space on the web is crowded and the incumbents have specific blind spots worth naming.

Bankrate runs one of the more complete affordability calculators on the SERP. Inputs for income, debt, down payment, rate, tax, insurance, HOA. Outputs a home-price ceiling with a payment breakdown. Defaults to the 28/36 conventional rule and buries the loan-type selector behind an expand; FHA and VA require hunting. No VA residual income, no self-employed mode, no comfort ceiling, no student-loan rule selector. Result pages are dense with lender-affiliate CTAs — the math is competent, the surrounding page is built for lender-lead capture.

Zillow's affordability calculator is tightly integrated with their home-listings product. You get a price ceiling plus a list of Zillow listings at that price — which is great for their funnel and distracting as a pure calculator. Math is 28/36 default with minimal customization. No VA residual, no student-loan rule switcher, no self-employed handling. Heavy push into Zillow Home Loans at every interaction.

NerdWallet has probably the strongest editorial content around an affordability calculator on the open web. Their explainer articles on the 28/36 rule, DTI, and closing costs are legitimately good. The calculator itself, though, is single-number: one ceiling, basic inputs, rate and DTI adjustable but no loan-type toggle, no residual, no comfort check. The calculator-to-affiliate-content ratio on the page is heavy.

Rocket Mortgage is a lead-capture wrapper. Minimal inputs, minimal outputs, immediate "apply now" CTA. The calculator exists to qualify you for their loan application flow. No loan-type transparency, no self-employed handling, no residual income.

Chase, Wells Fargo, and similar bank calculators fit the same mold as Rocket — purposefully basic, heavy CTA into the bank's mortgage pipeline. Acceptable if you already know you're applying with them; not useful for standalone analysis.

Calculator.net is functionally excellent for power users. Exposes the 28/36 levers, supports loan-type selection, customizable everywhere. Ugly 2005-era UI, dense ad footprint, no plain-English verdict, no self-employed mode, no residual. Developers and finance nerds land there happily; a first-time buyer bounces in confusion.

Dave Ramsey's affordability calculator takes a strong editorial position (25% of net take-home, 15-year loan, 20% down) and the calculator enforces it. Feature for some users, bug for others. No 28/36 comparison, no FHA/VA alternatives, no student-loan nuance. If you disagree with Ramsey's framing, the tool gives you nothing else.

Fidelity's affordability calculator is embedded in their broader financial-planning tools. 28/36 default, no loan-type variations, no self-employed mode, no residual. Built to feed their retirement-planning funnel.

Our version is the opposite of most of these: the calculator is the whole page, three ceilings are visible by default, and the surrounding content is reference material for the sub-rules the tool uses. Nothing to click if you don't want it. No lender hand-off, no affiliate pitch, no account.

The tradeoffs we made, honestly:

- No pre-qualification letter. That requires a credit pull plus a lender relationship. If you need a letter, go through a lender directly. Fannie Mae lists lender directories at fanniemae.com and HUD-approved FHA-experienced lenders are listed at hud.gov.
- No live rate feed. You type the rate your lender quoted or use the sensible 2026 default (6.75%). Bankrate's rate page publishes daily average rates if you want a reference number; the rate you'll actually get depends on credit, LTV, loan size, and state.
- No USDA, jumbo, or non-QM loan handling. USDA has geographic eligibility maps we don't encode. Jumbo (above the $806,500 conforming baseline) has county-specific loan limits and independent pricing. Non-QM products (bank-statement, DSCR, asset-depletion) have lender-specific rules that resist generic modeling. For any of those, talk to a lender who handles them.
- No credit-score-based rate estimation. The rate you type is the rate. We don't estimate "you'd probably get 6.5% with your 680 credit score" because credit-tiered rates vary wildly by lender, LTV, and product. Get rate quotes from three lenders instead.
- No local market context. We don't know if $450,000 buys a townhouse in Nashville or a studio in San Francisco. The calculator stays in math, not real-estate commentary.
- No mortgage recast, refinance, or extra-payment modeling on this page. Those are separate tools. Once you've figured out what you can afford, our mortgage calculator handles the payment-level math, and the refinance calculator handles the "should I refi later" question.

For the default case — what a lender will approve, what a conservative budget supports, and what you can actually live with — this is the clearest three-number answer on the open web. For anything past that, we'll happily name the specialist tool or the real professional that fits.