How much loan can you actually afford — based on your income, existing debt, and the debt-to-income ratio lenders use
This tool is for: Borrowers shopping for a personal, auto, or home loan and sizing the request · People considering a major purchase and testing whether the payment fits their budget · Anyone who wants to check a loan offer against a conservative DTI threshold
- The maximum monthly loan payment your income and existing debts can comfortably support
- The maximum loan amount that payment corresponds to at a given rate and term
- How raising or lowering the DTI ceiling changes the amount you can borrow
Formulas Used
Back-End Debt-to-Income (DTI) Ratio
DTI = (Total Monthly Debt Payments) / Gross Monthly Income
Where: DTI = Debt-to-income ratio, expressed as a percentage (%), Total Monthly Debt Payments = Sum of all recurring monthly debt obligations including the proposed new loan (USD), Gross Monthly Income = Pre-tax monthly income from all sources (USD)
Source: Consumer Financial Protection Bureau — Debt-to-income ratio guide ✓ Verified
Loan Amount from Monthly Payment (Reverse Amortization)
P = M × [1 − (1 + r)^−n] / r
Where: P = Maximum affordable loan principal (USD), M = Maximum affordable monthly payment (USD), r = Monthly interest rate (annual rate / 100 / 12) (decimal), n = Total number of monthly payments (months)
Source: Standard present-value-of-annuity formula — derived from amortization ✓ Verified
Key Insight
DTI is the single most important affordability gate lenders apply. Reducing a $300/month existing debt raises the affordable loan amount by roughly the same magnitude as a 1.5-percentage-point lower interest rate on a 60-month loan.
Frequently Asked Questions
What DTI ratio is considered safe?
Most lenders prefer a back-end DTI under 36%, with some mortgage products allowing up to 43% (the qualified-mortgage ceiling) or even 50% with compensating factors. At 28% or below, borrowing is considered conservative. Between 36% and 43%, approval depends on credit and reserves. Above 43%, most conventional products decline. The default 36% in this calculator reflects the widely-cited conservative back-end ceiling.
Is this a pre-approval?
No. Pre-approval requires a lender to pull your credit, verify your income and employment, and apply their specific underwriting guidelines. This calculator estimates the upper bound of what your income and existing debts can support — it does not check your credit score, assets, or down payment. Use the result as a starting point for lender conversations, not a commitment.
Why does the term length change the loan amount so much?
A longer term spreads the same monthly payment over more months, so the present value of the payment stream is larger. Doubling the term roughly doubles the affordable loan amount at the same monthly payment, but also roughly doubles the total interest paid over the loan life. A longer term raises your borrowing ceiling but increases total cost.
About This Calculator
Sources:
- Consumer Financial Protection Bureau — What is a debt-to-income ratio? — Official CFPB definition and methodology for the back-end debt-to-income ratio used by mortgage and consumer lenders
- Federal Trade Commission — Consumer Advice on Loans — Federal consumer-protection guidance on evaluating loan affordability and comparing offers
Limitations:
- Uses a single DTI ceiling — real lenders apply both front-end and back-end ratios and may set different ceilings per product
- Assumes fixed interest rate and standard amortization — variable-rate or interest-only products behave differently
- Does not include property taxes, insurance, HOA, PMI, or origination fees
- Maximum is a ceiling, not a target — prudent borrowers borrow below the ceiling
When to consult a professional: Before committing to a mortgage, consolidating debt, or borrowing more than 20% of annual gross income
This calculator estimates affordability using the debt-to-income (DTI) ratio. It does not guarantee loan approval. Lenders also evaluate credit score, employment history, down payment, reserves, and loan-specific guidelines. This is a planning tool, not financial advice.