How much of your income should go toward your mortgage payments?

How much of your income should go toward your mortgage payments?

Choosing a mortgage isn’t just about finding a loan amount that fits the property price. It’s about making sure the monthly payment is genuinely sustainable alongside your other living costs.

A useful way to think about affordability is to look at your mortgage payment as a percentage of your net (after-tax) income. While lenders will apply their own affordability checks, understanding the figures can help you budget more confidently and avoid stretching your finances.

What counts as a mortgage payment?

A mortgage payment is usually made up of more than just paying back the loan. Depending on the mortgage type and what’s included in your monthly outgoings, your payment may include:

• Principal (the amount you borrow)
• Interest (the cost of borrowing)
• Insurance (for example, buildings insurance)
• Taxes/other costs (for example, where certain costs are collected alongside the mortgage)

It’s also important to recognise that mortgage payments are ongoing commitments. Missing payments can quickly create serious financial consequences, so planning for the long term matters.

Repayment vs interest-only: why it affects your monthly cost

Most homebuyers choose between two broad mortgage structures:

• Repayment mortgages: your monthly payment covers interest and a portion of the loan, so the balance reduces over time.
• Interest-only mortgages: your monthly payment covers interest only, with the repayment of the original loan balance planned for later (for example, via a separate arrangement).

Because repayment mortgages reduce the loan balance, they often feel more “complete” from a budgeting perspective—though the monthly payment level will depend on the interest rate, term, and loan size.

The practical rules of thumb for mortgage affordability

There’s no single percentage that works for everyone. However, rules of thumb can help you sanity-check whether a mortgage payment is likely to leave enough room for day-to-day spending and unexpected costs.

The 28% rule (a cautious benchmark)

A commonly used guideline is to keep your mortgage payment to around 28% of your net monthly income.

Why this can be helpful:

• It leaves space for utilities, food, transport, childcare, and other essentials.
• It can make it easier to absorb changes such as higher bills or reduced income.
• It may reduce the risk of your mortgage becoming unmanageable if costs rise.

This approach is often seen as more conservative—particularly for first-time buyers who are still learning their true monthly cost of living in a new home.

The 35% to 45% range (a more flexible approach)

Another widely discussed guideline is to keep mortgage payments somewhere between 35% and 45% of net income.

This can be workable where:

• your other monthly commitments are relatively low
• you have a stable income and some savings buffer
• you’re confident you can manage changes in interest rates or household costs

However, the higher you go within this range, the more sensitive your budget can become to life events. Even a modest rise in living costs—or a change in interest rates when a deal ends—can push your spending pressure beyond what feels comfortable.

Why lenders may assess affordability differently

Even if you’re comfortable with your own percentage calculation, lenders will run their own affordability assessment.

In broad terms, lenders typically consider:

• Your income (often using gross income)
• Your regular outgoings (including existing debts)
• Your credit commitments (such as credit cards, loans, and other monthly obligations)
• Your mortgage payment under the terms they’re assessing

Because each lender’s methodology can differ, two borrowers with the same salary may see different outcomes depending on their circumstances and the specific mortgage product.

What influences how much your mortgage payment will be

Your mortgage payment percentage isn’t just about your income. It depends on several moving parts:

1) The interest rate you secure

Interest rate is one of the biggest drivers of monthly cost. Even small differences in rate can have a noticeable impact on payments, especially over longer terms.

2) The property value and loan size

The more you borrow, the higher your monthly payment is likely to be. A larger deposit can reduce the loan amount, which may help keep payments lower.

3) How much you can borrow

Your borrowing capacity is shaped by your income, outgoings, and existing commitments. It’s also influenced by the lender’s affordability model.

4) Mortgage term (length)

The term you choose affects the monthly payment level. Longer terms can reduce monthly payments, but may increase the total interest paid over the life of the mortgage.

Stress-testing your budget: what to consider beyond the headline percentage

A mortgage payment that looks fine today may become harder to manage if circumstances change. When working out what percentage of income to target, it can help to consider:

• Potential interest rate changes after a fixed deal ends
• Rising household costs such as energy bills, council tax, and groceries
• Changes in income (for example, reduced hours or career breaks)
• New commitments (childcare, travel, or other recurring expenses)

A useful affordability mindset is to ask: If costs rise, would the mortgage still feel manageable?

A simple way to check affordability before you apply

To get a clearer picture, you can:

1. Calculate your net monthly income (after tax).
2. Estimate your monthly mortgage payment for the mortgage you’re considering.
3. Work out the percentage: mortgage payment ÷ net income.
4. Compare it to a range (for example, around 28% as a cautious benchmark, or 35%–45% as a more flexible guideline).
5. Review your other essential spending to ensure there’s room for bills, lifestyle, and emergencies.

This doesn’t replace a lender’s affordability assessment, but it can help you avoid choosing a mortgage that leaves too little margin.

Key takeaway

A sensible mortgage payment percentage is one that supports a stable budget now and can cope with change later. While rules of thumb such as 28% or 35%–45% of net income can be useful, the most important factor is whether the payment fits comfortably alongside your real monthly costs and future uncertainties.