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Mortgage Affordability Calculator

A lender’s approval and the price you can live with are two different numbers. Enter your income, debts, and down payment to find your ceiling under the standard 28/36 rule — with property tax, insurance, HOA, and PMI counted, not just principal and interest.

What price house fits your budget?

Enter your numbers — the bar splits the monthly payment into principal & interest, tax, insurance, HOA, and PMI, and the gauge shows where the price sits between comfortable, stretch, and over-limit.

Gross annual income

Before taxes — everyone on the loan.

Monthly debts

Car, student, card minimums — everything but the mortgage.

Down payment %

Share of the price paid up front. Under 20% adds estimated PMI.

Mortgage APR %

The 30-year fixed rate you expect to get.

Loan term

Shorter term, bigger payment, less interest.

Property tax % / yr

Annual tax as a share of the price.

Insurance % / yr

Homeowners insurance as a share of the price.

HOA $ / month

Monthly association dues, if any.

Front-end DTI %

Max share of income for housing. Lenders use 28.

Back-end DTI %

Max share of income for all debts. Lenders use 36.

Down:

Maximum affordable home price$367,100About $2,333/mo housing payment (P&I $1,905 · tax $337 · insurance $92) · down payment $73,420 · estimated.

Where every dollar of the monthly payment goes. Change any input and watch the money move.

Front-end cap · 28%$367,139Housing only — the comfort ceiling

+$26,224back-end minus front-end ceiling

Back-end cap · 36%$393,363All debts, including existing ones

Your affordable ceiling is $367,100 — the 28% front-end rule binds: housing alone hits its limit before your other debts do. At that price expect about $2,333/mo and a $73,420 down payment.

Comfortable follows the 28% housing rule; stretch follows the 36% all-debts rule. The needle marks your affordable ceiling.

How it works: affordable price = (DTI budget − HOA) ÷ K, computed twice — once at the front-end cap (28% of monthly income) and once at the back-end cap (36% of monthly income minus your other debts) — keeping the lower price. K is the monthly cost of each dollar of price: (1 − down) × R for principal and interest, plus (tax rate + insurance rate) ÷ 12, plus estimated PMI of 0.5% of the loan per year when the down payment is under 20%. R = r ÷ (1 − (1 + r)^−n) is the amortization factor for the loan term. All figures are planning estimates, not a lending decision.

How mortgage affordability is calculated

Mortgage affordability comes down to two ratios lenders call DTI — debt-to-income. The front-end ratio caps your housing payment at about 28% of gross monthly income. The back-end ratio caps all of your monthly debts, mortgage included, at about 36%. Whichever ratio allows the lower price is your ceiling.

Housing payment here means the full PITI: principal and interest, property tax, and homeowners insurance — plus HOA dues and PMI when they apply. Most budget surprises in home buying come from the letters after PI: tax and insurance alone can add 20–30% on top of principal and interest.

The formulas

ceiling = min(front-end price, back-end price) · front-end price = (28% × monthly income − HOA) ÷ K · back-end price = (36% × monthly income − debts − HOA) ÷ K · K = (1 − down) × R + (tax + insurance) ÷ 12 (+ PMI when down < 20%) · R = r ÷ (1 − (1 + r)^−n)

K is the monthly cost of each dollar of price: the loan slice (1 − down) times the amortization factor R, plus tax and insurance sliced monthly. PMI adds about 0.5% of the loan per year when the down payment is under 20%. Divide each DTI budget by K and the lower price wins.

Worked example: $100,000 income, $500/mo in debts

Start with $100,000 gross income, $500/mo in other debts, 20% down, 6.75% APR on a 30-year loan, 1.1% property tax, and 0.3% insurance.

1. Monthly income: $100,000 ÷ 12 = $8,333.

2. Two budgets: front-end = 28% × $8,333 = $2,333/mo for housing; back-end = 36% × $8,333 − $500 = $2,500/mo.

3. Payment factor: at 6.75% over 30 years with 20% down, each $1,000 of price costs about $6.36/mo (P&I $5.19 + tax $0.92 + insurance $0.25).

4. Two prices: $2,333 ÷ 0.00636 ≈ $367,100; $2,500 ÷ 0.00636 ≈ $393,400. The 28% rule binds.

5. The check: $367,100 → loan $293,680 → P&I $1,905 + tax $337 + insurance $92 = $2,333/mo. Down payment: $73,420.

Where this comes in handy

Reading a pre-approval letter: lenders quote a maximum, often principal and interest only. Run the same income here to see the full-cost ceiling — then use the loan payment calculator to price the exact monthly payment.
Saving the down payment: 20% dodges PMI and buys more house per dollar of income. Feed the target down payment into the savings goal calculator to turn it into a monthly plan.
Checking what your paycheck really supports: affordability math starts from gross income, but the payment comes from net pay. The take-home pay calculator shows what actually lands in your account.
Comparing two loan offers: a lower rate buys a higher ceiling — roughly 9–10% more price per APR point on a 30-year loan. Put the terms head to head in the loan term comparison calculator.
Learning the method: the free how much house can I afford guide walks through the 28/36 rule, the five-step math, and the four costs that shrink every budget — step by step.

Mortgage Affordability Calculator — frequently asked questions

What is the 28/36 rule?

It is the affordability standard most lenders use. The front-end ratio says your housing payment — principal, interest, tax, insurance, HOA, and PMI — should stay at or under 28% of gross monthly income. The back-end ratio says all of your monthly debts together, mortgage included, should stay at or under 36%. The calculator prices your ceiling under both rules and keeps the lower one.

What counts as debts in the back-end ratio?

Car payments, student loans, credit-card minimums, child support, and alimony — anything with a fixed monthly bill. Groceries, utilities, subscriptions, and income taxes do not count; lenders ignore them. Paying off a $400/mo car loan raises the back-end ceiling by about $63,000 at today’s rates.

Why is my affordable price lower than my pre-approval?

Pre-approvals often stretch to the absolute maximum and may quote principal and interest only. This calculator prices the full monthly cost — tax, insurance, HOA, and PMI included — under both DTI caps, and it assumes you want the payment to fit, not just to be approved. Treat the pre-approval as a ceiling you are allowed to touch, not a target.

How much does PMI change the number?

Private mortgage insurance runs about 0.5% of the loan per year when the down payment is under 20%. On the worked example above, dropping from 20% to 10% down adds roughly $119/mo in PMI and trims the ceiling from $367,100 to about $316,200. Tap the down-payment chips above to watch it move.

Should I include my partner’s income?

Only if they co-sign the loan — the lender underwrites the combined income of the borrowers. If you are buying solo, enter your income alone: the payment has to fit your paycheck, not the household’s. Planning the down payment together is a different question, and there combining savings makes sense.

Does my credit score change the price?

Yes, through the interest rate: a better score can mean a meaningfully lower APR, and every point of APR shifts the affordable price by roughly 9–10% on a 30-year loan. Enter the rate you realistically expect — the calculator does the rest.

What if I have no debts at all?

Then the back-end cap rarely binds and the 28% front-end rule sets your ceiling. The comparison panel shows how far apart the two caps are — with zero debts the back-end budget runs about $667/mo above the front-end budget at $100,000 income. Watch the back-end take over as you add debts.

Is 28% actually comfortable, or just the maximum?

It is a lending ceiling, not a lifestyle recommendation. Lenders ignore utilities, maintenance, and savings when they size the loan, which is why 28% can still feel tight — budget another 1–2% of the price per year for upkeep on top. The zone gauge marks 28% as comfortable and 36% as stretch; treat anything past stretch as the red zone.

Learn the method: the free how much house can I afford guide walks through the 28/36 rule, the five-step math, and the four costs that shrink every budget — step by step.