Mortgage Affordability Calculator — How Much Can I Borrow?

A mortgage affordability calculator works out the most you could realistically borrow for a home, based on your income, deposit and existing debts. It answers the first question every buyer asks — how much can I borrow? — before you start viewing properties or applying to a lender.

The rules differ by country, so this tool has two modes. In the UK, lenders start from an income multiple (usually 4.5 times your gross annual income) and then run an affordability stress test, within limits set by the Bank of England and the FCA's MCOB 11.6 conduct rules. In Canada, lenders use two debt-service ratios — GDS and TDS — measured at a higher stress-test rate. It applies whichever set of rules matches the market you choose.

Use it to set a sensible budget, see how paying down a credit card or adding a joint applicant changes your borrowing power, and understand the loan-to-value that will unlock the best interest rates.

Your result above is driven by a handful of factors that every lender weighs up. Understanding them helps you see exactly why your number is what it is — and where you have room to improve it.

1. Your income

Income is the single biggest factor in how much can I borrow. Lenders start with your basic salary, then usually add regular overtime, bonuses and commission — often counted at 50%–100% depending on how consistent they are. If you are self-employed, most lenders average two to three years of accounts or tax returns, so try our dedicated self employed mortgage calculator for a closer estimate.

2. Your deposit or down payment and LTV

A larger deposit doesn't raise your income-based ceiling directly, but it lowers your loan-to-value (LTV) — the share of the price you're borrowing. A lower LTV unlocks better interest rates and can help you pass affordability. If you already own a home, check how much you could put down with our house equity calculator.

3. Monthly commitments and debts

Loans, credit cards, car finance, student loans and childcare all reduce your borrowing because lenders subtract them before working out what's left for a mortgage. This calculator applies the same principle: it deducts your annualised monthly commitments from income before applying the income multiple, which is a simplified version of how a lender's full affordability model works. Clearing debt before you apply is one of the fastest ways to improve how much you can afford. See how overpaying works on our loan overpayment calculator.

4. Credit score, employment type and age

A strong credit history opens more lenders and better rates; recent defaults or CCJs can cut borrowing by 10%–30%. Permanent employment is preferred over contract work, and lenders check you can repay before retirement — which caps the term available to older borrowers.

5. What percentage of income should go on your mortgage?

As a rule of thumb, most UK advisers suggest keeping your mortgage payment under roughly 35% of net (take-home) income, leaving room for bills, savings and the unexpected. Lenders themselves generally want your stressed repayment to stay under about 40–45% of gross income — which is exactly what the affordability check in the calculator above is testing.

If your result above is less than you hoped, these steps genuinely move the number:

Pay down existing debt. Reducing monthly commitments often boosts borrowing more than saving the same amount as deposit, because lenders assess outgoings, not just deposit size.

Save a larger deposit. This lowers your LTV and unlocks sharper interest rates.

Apply jointly. Combining two incomes usually increases borrowing substantially.

Document all income, including regular bonuses and overtime, and fix your credit report before applying.

Planning to buy your first home? Get a feel for lender decisions with our mortgage in principle calculator before you apply.

This tool works for every kind of applicant — here is how lenders treat the most common situations.

Joint mortgages

With a joint application, lenders use your combined income. For example, two people each earning £40,000 could borrow roughly £320,000–£360,000 together at 4–4.5×, versus about £160,000–£180,000 individually. Both applicants' credit and debts are assessed, so one person's issues can affect the whole application.

Self-employed applicants

Freelancers, contractors and company directors usually need one to three years of accounts (SA302s in the UK, T1/Notice of Assessment in Canada). Because many write off expenses, taxable income can look lower and reduce borrowing — a specialist lender or broker helps here. Estimate your figure on the self employed mortgage calculator.

First-time buyers

First-time buyers can sometimes access higher income multiples or lower deposits. If borrowing alone falls short, a guarantor mortgage calculator or a shared ownership mortgage calculator can show alternative routes onto the ladder.

UK mortgage affordability example

A couple with a combined income of £75,000, a £45,000 deposit and £250/month of commitments. At the standard 4.5× multiple (adjusted for their debts) this gives an estimated borrowing of around £320,000, giving a maximum property price near £365,000 — an LTV of roughly 88%. A specialist lender offering 5.5×–6.5× could push this higher for the right applicant profile.

Canada affordability example

A household earning $100,000 with a $60,000 down payment, $400/month of debts and a 4.29% rate over 25 years. With the stress test at 6.29%, the GDS ratio (39%) becomes the binding limit, giving a maximum mortgage near $423,000 and a home price around $483,000. Because the down payment is under 20%, CMHC insurance would apply.

Change any input in the calculator above and the results update instantly, so you can test how a bigger deposit, less debt or a joint application changes your number.

Affordability is what you can comfortably repay; qualification is the maximum a lender will actually offer after checking your credit, income and the property. This calculator estimates the qualification ceiling — always leave headroom for savings, emergencies and rate rises.

Once you know your budget, the usual next steps are: get an agreement in principle to show sellers you're serious; work out the real cost with our residential mortgage calculator; and, if you already own, compare deals on the remortgage calculator. Older homeowners exploring later-life options can also look at our equity release calculator. Browse every tool on the mortgage calculators homepage.

Official sources & further reading: UK borrowers can read the government-backed guidance at MoneyHelper and lending rules from the Financial Conduct Authority. Canadian buyers can check CMHC and the free Government of Canada Mortgage Qualifier tool.