Debt to Income Calculator

Debt to Income Calculator

A debt-to-income (DTI) calculator determines the percentage of your gross monthly income that goes toward debt payments. Lenders use DTI to assess your ability to manage mortgage payments.

DTI Ratio Types

Ratio	What It Measures	Formula
Front-End (Housing)	Housing costs only	(PITI) / Gross Income
Back-End (Total)	All debt payments	(Total Debt) / Gross Income

DTI Requirements by Loan Type

Loan Type	Max Front-End	Max Back-End
Conventional	28%	36-43%
FHA	31%	43%
VA	None	41%
USDA	29%	41%
Jumbo	28%	36%

DTI Calculator Implementation

``javascript function calculateDTI(grossMonthlyIncome, monthlyDebts) { // monthlyDebts object: { housing, carLoan, studentLoan, creditCards, other } const housing = monthlyDebts.housing || 0; const totalDebt = Object.values(monthlyDebts).reduce((sum, d) => sum + d, 0);

const frontEndDTI = (housing / grossMonthlyIncome) * 100; const backEndDTI = (totalDebt / grossMonthlyIncome) * 100;

let status; if (backEndDTI <= 36) status = 'Excellent - easily qualifies'; else if (backEndDTI <= 43) status = 'Good - qualifies for most loans'; else if (backEndDTI <= 50) status = 'Fair - may qualify with compensating factors'; else status = 'Poor - unlikely to qualify';

return { frontEndDTI: frontEndDTI.toFixed(1) + '%', backEndDTI: backEndDTI.toFixed(1) + '%', status, maxAffordableHousing: ((grossMonthlyIncome * 0.28) - housing).toFixed(2) }; }

const income = 8000; const debts = { housing: 1800, carLoan: 400, studentLoan: 300, creditCards: 100 }; console.log(calculateDTI(income, debts)); // { frontEndDTI: '22.5%', backEndDTI: '32.5%', status: 'Excellent' } ``

Improving Your DTI

Lower DTI by paying off debt (especially high-payment items like car loans), increasing income, or buying a less expensive home. Avoid new debt before applying for a mortgage.

Where the Money Goes

On $250,000 at 6% over 30 years, paying $1,499 a month:

Point	Principal repaid	Interest paid	Balance
Year 3	$9,790	$44,170	$240,210
Year 8	$28,200	$106,698	$221,800
Year 15	$72,378	$197,420	$177,622
Year 23	$141,584	$263,112	$108,416
Year 30	$250,000	$289,595	$0

Early payments are mostly interest. That is not a fee structure — it is arithmetic: interest accrues on the outstanding balance, which starts at its largest. It is also why an extra payment made early saves far more than the same payment made late.

What a Rate Change Costs

Rate	Monthly	vs 6%	Total repaid
5.00%	$1,342	-$157	$483,139
5.50%	$1,419	-$79	$511,010
6.00%	$1,499	—	$539,595
6.50%	$1,580	+$81	$568,861
7.00%	$1,663	+$164	$598,772

Half a percentage point moves the monthly payment by $81 and the total by $29,266. Shopping three lenders usually beats any amount of negotiating on price.

What an Extra Payment Buys

Every dollar above the required $1,499 goes entirely to principal, which removes all the future interest that principal would have accrued:

Extra per month	New payment	Paid off in	Interest saved	Time saved
$50	$1,549	27 yr 6 mo	$28,663	30 months
$100	$1,599	25 yr 6 mo	$51,572	54 months
$250	$1,749	21 yr 0 mo	$99,751	108 months
$500	$1,999	16 yr 5 mo	$146,128	163 months

The returns are non-linear because the saved interest compounds. It is also front-loaded: the same extra payment made in year one saves substantially more than in the final year, because it removes principal that would otherwise accrue interest for the whole term.

Before Paying Extra

• Check for a prepayment penalty. Uncommon on mortgages now, still present on some auto

and personal loans.

• Tell the servicer to apply it to principal. Many default to holding it as the next

scheduled payment, which achieves nothing.

• Compare against the alternative. Paying down 6% debt is a guaranteed

6% return. If you hold debt at a higher rate, or an employer match you are not taking, those come first.

• Keep the emergency fund. Money paid into a loan is not retrievable without

refinancing. Liquidity has value that an interest calculation does not show.