How much does a £300,000 mortgage cost?

If you’re considering borrowing £300,000, one of the first questions you’ll probably ask is: “What will my mortgage repayments be each month?”

The honest answer is that the cost of a £300,000 mortgage depends on a few moving parts—mainly the interest rate, repayment term, and whether you choose repayment or interest-only.

This guide helps you estimate what a £300,000 mortgage might cost, what income and deposit you may need, and what other costs to factor in.

What will a £300,000 mortgage cost per month?

Your monthly repayment is calculated using:

Loan amount (in this case, £300,000)
Interest rate
Mortgage term (e.g., 25 years)
Mortgage type (repayment vs interest-only)

Repayment vs interest-only (quick comparison)

Repayment mortgage: you pay back both the interest and the balance, so your monthly payment is higher but the loan is cleared by the end of the term.
Interest-only mortgage: you pay only the interest each month, so payments are typically lower—but you must repay the original £300,000 at the end of the term using a separate plan.

Mortgage repayment calculator (estimate your monthly cost)

Use the calculator below to estimate your monthly repayment and total cost.

Enter the loan amount you want to borrow, the interest rate you’re considering, and the term length.

Loan amount: £300,000 (or change if you’re comparing scenarios)

Mortgage rate:

Mortgage term:

Calculate

Once you’ve got an estimate, it’s worth stress-testing it—because even a small change in interest rate can noticeably affect monthly costs.

Example monthly repayments on a £300,000 mortgage

To give you a practical feel for the numbers, here are illustrative example repayments for a repayment mortgage at different interest rates and terms.

These figures are for guidance only. Your actual repayment will depend on the specific mortgage product, your rate, and any fees.

Interest rate	15 years	20 years	25 years	30 years	35 years
1%	£1,795	£1,380	£1,131	£965	£847
2%	£1,931	£1,518	£1,272	£1,109	£994
3%	£2,072	£1,664	£1,423	£1,265	£1,155
4%	£2,219	£1,818	£1,584	£1,432	£1,328
5%	£2,372	£1,980	£1,754	£1,610	£1,514
6%	£2,532	£2,149	£1,933	£1,799	£1,711
7%	£2,696	£2,326	£2,120	£1,996	£1,917
8%	£2,867	£2,509	£2,315	£2,201	£2,131

If you’re considering interest-only

With an interest-only mortgage, the monthly payment is driven by the interest rate and the loan balance. It does not reduce over time in the same way as a repayment mortgage.

How much income do you need for a £300,000 mortgage?

Lenders use affordability checks and income assessments to decide how much they’ll lend.

A common starting point is that many lenders consider salary multiples (often around 4 to 4.5 times your combined annual income), but this is not a guarantee—your outgoings, credit profile, and other factors can all affect what’s offered.

Rough income guide (illustrative)

If lenders used a 4x–4.5x multiple, you might be looking at:

4x income: £75,000 per year to borrow £300,000
4.5x income: about £66,667 per year to borrow £300,000

If you don’t fit comfortably within those ranges, a broker can help you explore options such as joint applications, different term structures, or mortgage types that may suit your situation better.

Mortgage affordability calculator (estimate what you could borrow)

If you want to work backwards from your income, use this affordability calculator to estimate borrowing potential based on typical salary multiples.

Total household income (yearly, before tax):

Include income such as salary, bonuses, overtime, and other regular earnings where applicable.

How much deposit do you need for a £300,000 mortgage?

A deposit is usually based on the property price, not the mortgage amount.

As a guide, many borrowers aim for a deposit in the region of 5% to 10% of the property value, depending on the lender and mortgage product.

Example deposit scenarios

If the property is £300,000 and you put down 5%, your deposit would be £15,000 and you’d borrow £285,000.
To borrow £300,000, the property value would typically need to be higher than £300,000 if you’re only putting down a 5%–10% deposit.

Why deposit size matters

In general:

A higher deposit can mean a lower loan-to-value (LTV).
Lower LTVs often give you access to more competitive mortgage pricing.
A bigger deposit can also reduce monthly repayments.

LTV calculator (check your loan-to-value)

Use this to estimate your LTV based on:

Property value
Deposit/equity
Loan amount

A lower LTV may help you access a wider range of mortgage options.

Factors that affect the cost of a £300,000 mortgage

Even with the same loan amount, your monthly cost can change due to:

1) Interest rate

The rate you’re offered is one of the biggest drivers of monthly repayments.

2) Mortgage term length

Shorter terms usually mean higher monthly payments but less interest overall.
Longer terms usually reduce monthly payments but increase total interest paid.

3) Repayment method

Repayment vs interest-only can make a significant difference to your monthly outgoings.

4) Your credit history and affordability profile

Lenders may price risk differently and apply affordability rules based on your circumstances.

5) Fixed vs tracker (if available)

If you choose a fixed rate, your payment may be more predictable for the fixed period. Tracker rates move with a reference rate.

Other costs to budget for (beyond monthly repayments)

When you’re planning the true cost of buying, don’t forget the upfront and ongoing expenses that can sit alongside your mortgage.

Common upfront costs

Valuation/survey costs (depending on the level of survey you choose)
Mortgage fees (some products have arrangement/product fees)
Conveyancing fees (legal work for the purchase)
Stamp Duty Land Tax (based on the property and your circumstances)

Ongoing costs

Buildings insurance (usually required)
Life insurance / income protection (optional, but often considered to protect affordability)

How a mortgage broker can help with a £300,000 mortgage

A broker can help you narrow down options by matching your situation to lenders and products that fit your needs.

They can also help you:

compare repayment scenarios across term lengths and mortgage types
understand how deposit and LTV may affect pricing
prepare for lender questions and documentation requirements
review the total picture—monthly cost, upfront fees, and long-term affordability

Ready to estimate your repayments more accurately?

If you’d like a clearer idea of what a £300,000 mortgage could cost you based on your term, deposit and the type of mortgage you’re considering, speak to our advisers. We’ll help you model the options and find a mortgage route that fits your circumstances.

How much does a £300,000 mortgage cost?