Question 1

What is the 28/36 rule in mortgage lending?

Accepted Answer

The 28/36 rule is a standard debt-to-income (DTI) guideline used by mortgage lenders: housing expenses should not exceed 28% of gross monthly income, and total debt payments should not exceed 36%.

Question 2

What counts toward the 28% front-end ratio?

Accepted Answer

The front-end ratio includes PITI: mortgage principal, interest, property taxes, homeowners insurance, plus HOA dues and private mortgage insurance (PMI).

Question 3

What counts toward the 36% back-end ratio?

Accepted Answer

The back-end ratio includes all housing costs from the front-end ratio PLUS auto loans, student loans, minimum credit card payments, personal loans, and alimony/child support.

Question 4

Can you show a worked calculation for a $9,500/month income?

Accepted Answer

With $9,500 gross income: 28% front-end cap is $2,660/mo. 36% total debt cap is $3,420/mo. If you have $750/mo in car and student debts, allowable housing under back-end is $2,670 ($3,420 - $750). The binding cap is $2,660/month, qualifying you for approximately a $420,000 home.

Question 5

Do all lenders strictly enforce the 28/36 rule?

Accepted Answer

No. While 28/36 is the gold standard for prime conventional loans, FHA loans allow back-end DTIs up to 43% (and 50% with compensating factors), and VA loans allow up to 41%.

Question 6

Are my salary and debt numbers private on ToolboxDock?

Accepted Answer

Yes. All DTI underwriting calculations execute locally in your web browser with zero server data collection.

Question 7

How can I increase my borrowing power under the 28/36 rule?

Accepted Answer

Paying off high monthly recurring debts (such as car loans or credit cards), improving credit score to lower APR, or increasing your down payment directly expands your allowable home purchase price.

Guideline Standard	Front/Back %	Max Housing (PITI)	Total Debt Ceiling
Conservative (25/33 Rule)	25/33%	$2,375	$3,135
Standard Conventional (28/36 Rule)	28/36%	$2,660	$3,420
FHA Maximum (31/43 Rule)	31/43%	$2,945	$4,085
Aggressive / Jumbo (35/45 Rule)	35/45%	$3,325	$4,275

Evaluation Criteria	ToolboxDock (Client-Side)	Traditional Online Calculators
Financial Data Privacy	100% Local (Never leaves device RAM)	Logged on remote servers and ad networks
Calculation Latency	Instant real-time update on keystroke	Full page reloads or API round-trips
Offline Usability	Works offline once cached in browser	Fails without active server connection
Cost & Paywalls	100% free with unlimited calculations	Usage caps or financial product paywalls

Guideline Standard	Front/Back %	Max Housing (PITI)	Total Debt Ceiling
Conservative (25/33 Rule)	25/33%	$2,375	$3,135
Standard Conventional (28/36 Rule)	28/36%	$2,660	$3,420
FHA Maximum (31/43 Rule)	31/43%	$2,945	$4,085
Aggressive / Jumbo (35/45 Rule)	35/45%	$3,325	$4,275

28/36 Rule Debt Calculator

Income & Debt Profile

$2,660per month max

Front-End (28% Cap)

Back-End (36% Cap)

Max Purchase Price

Mortgage Underwriting Guidelines Matrix

What is the 28/36 Rule Debt Calculator?

Financial Calculation Inputs

Output & Schedule Breakdown

How to Use the 28/36 Rule Debt Calculator

1. Enter Gross Monthly Income

2. Input Recurring Non-Housing Debts

3. Set Down Payment & Interest Rate

Financial Privacy & Architecture Comparison

The 28/36 Underwriting DTI Formula

Frequently Asked Questions

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