DTI Calculator — Debt to Income 28/36 Rule Mortgage

What Is a DTI Calculator – Debt to Income 28/36 Rule Mortgage?

A DTI calculator measures debt to income ratio — how much of your gross monthly income goes to housing and debts. Lenders in the U.S. use DTI to gauge affordability. This version uses the classic 28/36 rule referenced by CFPB, FHFA, and traditional underwriting guides.

Front-end DTI (housing ratio): Housing expense / gross monthly income. Housing includes principal + interest + taxes + insurance + PMI + HOA. Classic guideline ≤28%. Example: $10,000 gross income, 28% = $2,800 max housing.

Back-end DTI (total debt ratio): (Housing + all recurring debts like auto, student loan, credit card minimums) / gross income. Classic guideline ≤36%. Actual lender guidelines vary — conventional often allows up to 45-50% with strong credit per Fannie Mae, FHA allows higher with compensating factors. This calculator focuses on front-end; for back-end add other debts separately.

This calculator shows estimated monthly payment with taxes, insurance, PMI, HOA, cash to close with down + closing fees, and front-end DTI check against 28/36 guideline.

How To Use This DTI Calculator

Step 1: Enter home price and location. Example: $600,000 home. State/ZIP optional — e.g., California or 90210 — used for note only, not tax lookup. Use actual purchase price, not rounded. Loan term — 30 year fixed typical, 15 year lower interest higher monthly.

Step 2: Enter down payment %, interest rate %, annual tax, annual insurance, PMI rate, HOA monthly. Down payment % — 20% avoids PMI, less than 20% triggers PMI. Interest rate — e.g., 6.75% — enter your quoted rate. Annual tax — e.g., $6,000 — check county assessor, not national average. Annual insurance — e.g., $1,800 — use actual quote. PMI rate %/yr — e.g., 0.75% typical if down <20%, actual varies 0.3% to 1.5% by credit. HOA monthly — e.g., $0 if no HOA, $300 if condo.

Step 3: Enter gross monthly income for 28/36 check — e.g., $10,000/mo = $120k annual gross. Use gross before taxes, not take-home. Lenders use gross per CFPB. If income is $0, DTI shows 0% and check notes affordable per rule logic handling.

Step 4: Press Calculate Payment and Affordability. Review total monthly cost, principal + interest, tax, insurance, PMI+HOA, cash to close down + 2.9% closing fees estimate, and front-end DTI % with within/above 28% badge. Try down 20% vs 10% to see PMI impact, or rate 6.75% vs 7.5% to see monthly change.

How It Calculates — Formula & Methodology

Source: Standard mortgage amortization formula used by CFPB, FHFA, and HUD for PITI + PMI + HOA.

M = P [r(1+r)^n]/[(1+r)^n-1] — Total = M + tax/12 + insurance/12 + PMI + HOA — DTI = Total / income × 100

P = loan amount = price × (1 – down%/100), r = monthly rate = APR/12/100, n = months = term years × 12, M = principal + interest.

Steps with example numbers — inputs $600,000 price, 20% down, 6.75% rate, 30yr, tax $6,000, insurance $1,800, PMI 0.75%, HOA $0, income $10,000:

1. Loan P = 600,000 × (1 – 0.20) = $480,000
2. r = 6.75 / 12 / 100 = 0.005625, n = 30 × 12 = 360
3. (1+r)^n = (1.005625)^360 = 7.553
4. M = 480,000 × (0.005625×7.553)/(7.553-1) = 480,000 × 0.006483 = $3,112
5. Tax monthly = 6,000/12 = $500, Insurance monthly = 1,800/12 = $150, PMI = down <20%? No — 20% = 0, HOA 0
6. Total = 3,112 + 500 + 150 + 0 + 0 = $3,762
7. Front-end DTI = 3,762 / 10,000 × 100 = 37.6% — Above 28% guideline by 9.6% — $962 over 28% max $2,800
8. Cash to close = down 20% $120,000 + closing 2.9% $17,400 = $137,400

If down 10% instead of 20%: Loan $540,000, M $3,501, PMI = 540,000 × 0.75%/12 = $337.50, total $4,488.50, DTI 44.9% — higher due to PMI + larger loan. If rate 0%: M = loan/n = 480,000/360 = $1,333, total $1,983, DTI 19.8% within 28%.

Methodology notes: If rate 0%, uses loan/n. If loan 0, PI 0. If income 0, DTI 0% to avoid Infinity. Results browser-side. USD format. Closing 2.9% estimate — actual varies by state, lender, title, escrow.

What Results Mean

Your Estimated Monthly Cost: Total PITI + PMI + HOA — principal + interest + tax + insurance + PMI + HOA — e.g., $3,762/mo.

Principal + Interest: Base mortgage payment from amortization — e.g., $3,112/mo for $480k at 6.75% 30yr.

Tax: Annual tax /12 — e.g., $6,000/12 = $500/mo — check county assessor, not estimate.

Insurance: Annual insurance /12 — e.g., $1,800/12 = $150/mo — use actual quote.

PMI + HOA: PMI if down <20% = loan × PMI rate /12 + HOA — e.g., 0.75% on $480k = $0 when down 20%, $337.50 when down 10% — HOA added directly.

Estimated Cash to Close: Down payment + closing fees — e.g., 20% down $120k + 2.9% closing $17,400 = $137,400 — includes title, escrow, lender fees estimate — actual varies.

Front-end DTI Badge: Total / income ×100 — e.g., 37.6% — Within 28% green, Above 28% red — shows $ amount over/under 28% max.

28/36 Affordability Check: Explains income $10k/mo, 28% max $2,800, 36% max $3,600 total debt, your housing $3,762, status above/below — educational, not approval.

Example — Worked Scenario

Inputs matching calculator defaults:

• Home Price: $600,000
• State/ZIP: Optional — e.g., California
• Loan Term: 30 Year Fixed
• Down Payment: 20%
• Interest Rate: 6.75%
• Annual Tax: $6,000
• Annual Insurance: $1,800
• PMI Rate: 0.75%/yr
• HOA Monthly: $0
• Gross Monthly Income: $10,000

Outputs:

• Loan Amount: $480,000
• Principal + Interest: $3,112/mo
• Tax: $500/mo, Insurance: $150/mo, PMI+HOA: $0
• Total Monthly: $3,762/mo
• Front-end DTI: 37.6% — Above 28% by 9.6% ($962 over)
• Cash to Close: ~$137,400

If down 10% $60k: Loan $540k, PI $3,501, PMI $337.50, total $4,488.50, DTI 44.9% — $1,688 over 28%. If income $15k/mo: 28% max $4,200, your $3,762 housing within 28% by $438 — DTI 25.1% — affordable per rule. Shows how down and income affect affordability.

Common Mistakes

1. Using net income not gross: 28/36 rule uses gross monthly before taxes per CFPB. If you use take-home $7k instead of gross $10k, DTI looks higher incorrectly. Use gross W2 + overtime + bonus per lender guidelines.
2. Forgetting PMI when down <20%: $600k price 10% down = $540k loan, PMI 0.75% = $337.50/mo extra — not including it underestimates total by $337.50. If down ≥20%, PMI 0 — but many forget to add it when down 15%.
3. Ignoring taxes and insurance: PITI not just PI — tax $6k/yr $500/mo + insurance $150/mo = $650/mo — ignoring makes payment look $3,112 not $3,762 — 21% low. Check county tax assessor, insurance quote.
4. Assuming 28/36 is approval guarantee: 28/36 is classic guideline, not current lender max. Conventional allows up to 45-50% back-end with strong credit, FHA allows higher. DTI within 28% does not guarantee approval — credit, LTV, reserves matter. Check Loan Estimate.
5. Using rounded home price not actual: $600k vs $625k changes loan $20k, PI $130/mo. Use exact purchase price, exact down %, exact rate quote — small changes move DTI 1-2%.

Practical Tip

If DTI is above 28%, try three tweaks in calculator: increase down from 10% to 20% to remove PMI $337/mo and lower loan, reduce price from $600k to $550k saves ~$313 PI + $50 tax, or increase income documentation — e.g., include spouse income if co-borrower. Aim for 20-25% buffer under 28% — if 28% max $2,800 on $10k income, target $2,200-$2,400 to leave room for utilities, maintenance, and back-end debts. Always verify with lender pre-approval — they calculate back-end DTI including auto, student, credit card minimums — your front-end may be 28% but back-end could be 45% if other debts high.

Important Limitations

This calculator provides estimates for educational and budgeting purposes. It is not loan offer, approval, rate quote, or affordability guarantee. It does not include HOA transfer fees, Mello-Roos, supplemental tax, earthquake insurance, flood insurance, or other costs that may apply in California, Florida, Texas, New York. PMI rate capped at 0% to 5% for safety — actual varies 0.3% to 1.5% by credit and LTV. Closing costs estimate 2.9% — actual varies 2% to 5% by state, lender, title. DTI 28/36 is classic guideline — actual lender guidelines vary by loan program — conventional, FHA, VA, USDA have different max DTI. Always verify with Loan Estimate, Closing Disclosure, county assessor, insurance quote, and lender DTI calculation.

Assumptions used in this page: Down payment % of price — presentation for cash to close, not including seller credits. PMI calculation as loan × annual rate /12 if down <20% — typical but actual PMI may use different tiers and may be upfront + monthly. Tax and insurance divided by 12 — actual escrow may include cushion. No assumption of rate lock, points, or buydown — rate entered as is. Gross monthly income for 28/36 — per traditional guideline — actual lender may use different income calculation.

Frequently Asked Questions

What is 28/36 rule for DTI calculator?

28/36 is classic affordability guideline: housing expense (PITI + PMI + HOA) should be ≤28% of gross monthly income (front-end DTI), total debt including housing + auto + student + credit card minimums should be ≤36% of gross (back-end DTI). Example $10k income, 28% = $2,800 max housing, 36% = $3,600 max total debt. Actual lender guidelines vary — conventional often allows 45-50% back-end, FHA allows higher with compensating factors. This calculator shows front-end only — add other debts for back-end.

How accurate is this DTI calculator for monthly payment?

It uses standard mortgage amortization M = P[r(1+r)^n]/[(1+r)^n-1] for principal and interest plus taxes, insurance, PMI, HOA. Accuracy depends on inputs you provide. It does not include supplemental tax, Mello-Roos, flood insurance, or HOA transfer fees. For final figures, use your lender's Loan Estimate. Tax and insurance should be from county assessor and insurance quote, not national averages.

What is front-end vs back-end DTI?

Front-end DTI = housing payment / gross monthly income — e.g., $3,762 / $10,000 = 37.6%. Back-end DTI = (housing + all other monthly debts) / gross income — e.g., if housing $3,762 + auto $400 + student $300 + cards $200 = $4,662 / $10,000 = 46.6% back-end. This calculator shows front-end — for back-end add other debts manually: back-end = (total housing + other debts) / income ×100.

How is PMI calculated in this DTI calculator?

PMI monthly = loan amount × PMI annual rate / 12 if down <20%. Example $540k loan × 0.75%/12 = $337.50/mo. If down ≥20%, PMI = 0. Assumption 0.75% annual typical — actual PMI varies 0.3% to 1.5% by credit score, LTV, loan program. Some loans have upfront PMI + monthly. Check Loan Estimate for actual PMI. Assumption: PMI calculated as annual % of loan — presentation for estimate.

What is cash to close and why 2.9%?

Cash to close estimated as down payment + closing costs. This calculator uses 2.9% of price for closing fees as estimate — e.g., $600k × 2.9% = $17,400. Plus down 20% $120k = $137,400 total. Actual closing costs vary 2% to 5% by state, lender, title, escrow, prepaid tax/insurance, discount points. Includes title, lender fees, escrow, prepaid items estimate — not exact. Verify with Closing Disclosure.

Does this calculator save my data?

Calculation runs in your browser. Inputs are not sent to a server. When you close or reload, inputs reset unless you saved them. No storage claim: browser calculation — check actual JS data flow if you use analytics or ads on page, those may collect separate data per your site privacy policy.