Debt-to-Income Ratio Calculator: UK and US Mortgage Limits (2026)

Debt-to-Income Ratio Calculator — What Lenders Actually See

Written by Hamid Ali, MSc Accounting & Finance · Founder of DebtShift · Updated 3 November 2026

You’ve got a good credit score. A clean payment history. And you still got turned down for a mortgage, or offered far less than you expected. The number that killed the application isn’t the one you’ve been watching — it’s your debt-to-income ratio, and most people find out what it is for the first time when a lender already has.

This calculator shows you exactly where you stand before you apply for anything, on both sides of the Atlantic.

Jump to: How UK lenders count debt · US limits · FAQ

What This Calculator Actually Does

Enter your gross monthly income and your monthly payments on housing, credit cards, loans, car finance, student loans and other debts, then choose UK or US. It shows the ratio of debt payments to income. The US result is compared with common US lender guidelines. UK lenders do not use one fixed DTI limit, so the UK result is a rough guide only.

\u2713 Free to use. No account, no sign-up and no bank link. You only give an email if you choose to have your result sent to you.

Who This Is For

Anyone preparing to apply for a mortgage, car finance, or any major loan who wants to know their real number before a lender pulls it. It’s also for anyone who’s already been rejected or offered less than expected and wants to understand why, since DTI is rarely explained clearly at the point of rejection.

How to Use It — UK

Enter your gross monthly income (your annual salary divided by 12) and every monthly debt commitment: credit cards, car finance, personal loans, student loan repayments. UK lenders do not use a fixed DTI percentage the way US lenders do. They run an affordability check and often cap the loan as a multiple of your income, typically around 4 to 4.5 times. Your existing debt payments are taken into account when they work out what you can afford.

How to Use It — US

Enter your gross monthly income and total monthly debt payments, including your proposed new mortgage payment if you’re applying for one. The calculator shows your back-end DTI and compares it against the real thresholds for each loan type — conventional, FHA, and VA all use different ceilings.

How UK Lenders Actually Count Your Debt

Three things happen when you apply, and none of them is a single DTI percentage.

• An income multiple sets the ceiling. Most lenders offer around 4 to 4.5 times your income. Until October 2026 the Bank of England capped each lender at 15% of new lending at 4.5 times income or more. That per-lender cap was removed on 28 October 2026, so each lender now decides how much high-multiple lending to do, although an overall limit across the market still applies.
• Your commitments are deducted first. Loan, car finance and card payments reduce the monthly amount a lender thinks you can afford. Some lenders also assume a minimum monthly cost for credit card balances, even if you clear the card each month, so a large balance can cost you borrowing capacity.
• Each lender does it differently. The same person can get a very different offer from two lenders, which is why a broker can be worth asking before you apply.

The quickest way to improve the result is to clear or shrink the debts with the highest monthly payment relative to the balance, such as car finance or a loan with a short term.

UK — Why There’s No Single “Good DTI” Number

Every lender works this out differently, so there is no standard formula. In general, the more you pay out each month on existing debt, the less a lender will say you can afford to borrow, so clearing a debt before applying can raise your borrowing capacity. By how much depends on the lender, so ask a broker or check with the lender before you apply.

US — The Real Thresholds by Loan Type

• Conventional (Fannie Mae) — 36% on manual underwriting, up to 45% with strong credit and reserves, up to 50% through automated underwriting
• FHA — 31% front-end / 43% back-end standard, rising to 40%/50% with compensating factors
• VA — no hard cap; uses 41% as a guideline but leans more heavily on residual income

If a lender tells you “43% is the max,” they’re quoting FHA specifically, not a universal rule — which loan type you’re applying for can change your real ceiling by 10 to 15 percentage points.

A Real Example

UK: gross income £45,000 is £3,750 a month. With £400 a month of existing debt payments, the ratio is £400 ÷ £3,750 = 10.7%. At an income multiple of 4.5, the headline maximum would be £202,500, before the lender takes your debt payments into account. The final figure depends on the lender, so it will be lower.

US: $2,500 proposed mortgage payment + $400 car loan + $200 student loan minimum = $3,100 total monthly debt. Divided by $7,000 gross monthly income = 44.3% DTI — above the standard conventional manual-underwriting limit, but within FHA-approvable territory given the right compensating factors.

What Actually Moves the Number

• Pay down credit cards first — they typically carry the heaviest weight per pound or dollar owed in most affordability models
• Avoid new credit before applying — new accounts and hard searches appear on your file and add to your monthly commitments.
• US: pay off installment loans with fewer than 10 payments left — many lenders exclude these from the calculation entirely once that close to finished
• Know your number before you apply — a wasted application to a lender who was never going to say yes costs you a hard credit check for nothing

Where the Numbers Come From

Checked October 2026. The ratio is monthly debt payments ÷ gross monthly income. The US example: ($2,500 + $400 + $200) ÷ $7,000 = 44.3%. The 28/36 guideline, FHA 31/43 and VA 41% figures are common lender guidelines, not laws. The old 43% qualified-mortgage limit was replaced by a price-based test in 2021, and St. Louis Fed (June 2026) found that mortgage denial rates rise sharply above a 50% ratio. UK lenders assess affordability individually, and the Bank of England 3 percentage point stress test was withdrawn in 2022.

If your debt payments are already hard to keep up with, free help is available from StepChange (0800 138 1111) in the UK and the NFCC in the US. This tool gives general information, not personal financial advice.

Related Tools

If your DTI needs work before applying, run your consolidation options through the Consolidation Reality Check, or see your full payoff timeline with the AI Debt Payoff Planner.

Frequently Asked Questions

Is there an official UK DTI percentage for mortgages?
No. UK lenders use an income multiple combined with an affordability stress test, not a published DTI cap like US lenders. Your debt still matters — it’s just factored in differently, through reduced borrowing capacity rather than a hard ratio limit.

What’s the maximum DTI to qualify for a US mortgage?
Depends on the loan type. Conventional caps around 36–50%, FHA up to 43–50% with compensating factors, VA has no hard cap but uses 41% as a guideline alongside residual income.

Does my rent count toward US DTI?
No. Current rent is dropped entirely and replaced by your proposed new mortgage payment once you’re applying to buy.

Should I pay off debt before applying for a mortgage?
Usually yes, if realistic — in both regions, clearing even one meaningful debt can materially change either your UK borrowing capacity or your US DTI percentage, sometimes enough to shift which loan products you qualify for entirely.