Debt-to-Income Ratio Calculator

Where DTI sits in a lending decision

When a lender assesses a mortgage application, two checks usually run in parallel: affordability (can the income cover the new payments?) and debt service (is the borrower already heavily committed?). Debt-to-income ratio is one summary of both. Commonly cited orientation ranges treat DTI above 43% as the level where many lenders become cautious, and above 50% as the level where mainstream approvals become uncommon. The calculator above produces that ratio.

Two DTI ratios, not one

Two different ratios often travel under the same name, and the distinction matters.

Front-end ratio (housing DTI): monthly housing costs (mortgage, local property tax, insurance, maintenance reserve) divided by gross monthly income. The commonly cited reference point is 28%, the front-end half of the 28/36 rule.

Back-end ratio (total DTI): all debt payments (housing, car loans, credit card minimums, student loans, personal loans) divided by gross monthly income. Commonly cited orientation ranges put under 36% as healthy, 36–43% as stretched, 43–50% as pressured, and above 50% as beyond common lender bands.

Lenders typically use the back-end ratio for approval decisions. A low back-end ratio alongside a high front-end ratio indicates housing costs dominate the total; the reverse indicates non-housing debt does.

The 28/36 rule

The 28/36 guideline pairs a 28% front-end ratio with a 36% back-end ratio. It is widely attributed to mortgage-industry practice rather than regulation, and many lenders apply similar logic internally. Stated as back-end thresholds alone: under 36% is the healthy band, 36–43% is the range where additional scrutiny is commonly described, and above 43%, more so above 50%, is where mainstream lending is commonly described as harder to obtain. The specific cutoffs vary by country, lender and product type.

Gross income or net income?

DTI is conventionally calculated on gross (pre-tax) income because lenders compare applicants against a standardised figure while tax positions vary. For personal budgeting the net figure is closer to lived experience, and the relationship between the two is arithmetic: net DTI equals gross DTI divided by the ratio of net income to gross income. At a 35% gross ratio with net income at 76% of gross, the net ratio is 46.05%. Where deductions are heavier and net income is 65% of gross, the same 35% gross ratio becomes 53.85% on net. The gross figure is what lenders standardise on; the net figure is what a bank statement reflects.

What counts as debt in the calculation

Typically included: mortgage payments, second-mortgage or home-equity borrowing, auto loan payments, minimum credit card payments, personal loan payments, student loan payments, court-ordered maintenance obligations, and other regular debt service. Typically excluded: rent (though some lenders count it), utilities, insurance unless bundled with housing, subscriptions, and one-off expenses. Business debts in a self-employed context are usually assessed separately by the lender. Where an item is ambiguous, including it produces a higher ratio than excluding it, and lenders verify the underlying commitments during underwriting.

The committed vs discretionary extension

A refinement some financial planners use separates committed debt (mortgage, car loan on a necessary vehicle) from discretionary debt (credit card balances from lifestyle spending, consumer loans for non-essentials). Two households at an identical 40% DTI can hold very differently structured portfolios. Committed debt is typically cheaper and harder to remove; discretionary debt is typically more expensive and more open to restructuring.

DTI and credit availability

Lenders that score both DTI and credit utilisation (the share of available credit in use) read the same ratio differently depending on the second figure. A borrower at 35% DTI using 90% of available credit and a borrower at 40% DTI using 30% present different profiles, because the available headroom differs. In markets where a utilisation guideline is applied, 30% is a commonly cited reference point. Paying down a credit card balance moves both figures at once.

Mortgage affordability beyond DTI

Mortgage lenders typically run something more granular than DTI alone: a detailed income-and-outgoings assessment covering fixed commitments, childcare and discretionary spending. The DTI figure summarises that picture rather than replacing it. Some markets also apply an income-multiple cap (around 4 to 4.5 times gross income is commonly cited) together with a stress test at a rate above the current fixed rate. Both the multiple and the stress margin vary by jurisdiction, lender and product type, so the ratio at the current rate is not the only figure being assessed.

Three approaches that shift the ratio

Paying down debt. The effect is largest on debts with high minimum payments relative to balance. Clearing a balance equal to one month’s gross income moves DTI by the minimum-payment rate itself: at a minimum payment of 1–3% of the balance, that is 1–3 percentage points. The figure is the same at any income level, because the balance and the income scale together.

Increasing income. A pay rise, job change or additional income source lowers the ratio by raising the denominator. The size of the shift depends on the rise relative to existing income.

Extending loan terms. Moving a 3-year car loan to 5 years lowers the monthly payment and therefore the ratio, while raising total interest paid over the life of the loan. It changes the monthly figure without reducing the underlying debt.

What the calculator shows

The tool computes the back-end DTI from the income and debt payments entered, and reports the housing share of income alongside it as the front-end ratio. It does not distinguish committed from discretionary debt, and the band shown alongside the result applies to the back-end ratio only.