Interest rate
A higher rate increases the interest charged on the outstanding balance and normally increases the monthly repayment.
MORTGAGE GUIDE
How much does a £300,000 mortgage cost?
The monthly payment depends on the interest rate, mortgage type and term. The same £300,000 balance can produce very different monthly payments and total costs when any of those inputs change.
WHAT CHANGES THE PAYMENT?
Rate and term are the main mathematical levers.
Term
A longer term spreads the repayment over more months. That can reduce the monthly payment but often increases total interest.
Mortgage type
Repayment gradually reduces the principal. Interest-only keeps the principal outstanding under the simplified model and therefore requires a separate capital-repayment plan.
A £300,000 EXAMPLE
Compare the scenarios rather than searching for one universal monthly figure.
Suppose the mortgage balance is £300,000 and the illustrative annual rate is 4.5%. A 25-year repayment term produces a different monthly payment from a 35-year term because the balance is spread across different numbers of payments.
Why this matters: the longer-term option can make the monthly payment look easier while increasing the number of months during which interest is charged. That is why the useful comparison includes both monthly payment and total interest.
The exact figure should always be recalculated using the rate, term and balance from the real mortgage illustration.
DEPOSIT & OVERPAYMENTS
The £300,000 figure may not be the amount you borrow.
If the property costs £300,000 and you have a £30,000 deposit, the mortgage starts at £270,000 in the simple purchase-price model. Use the 10% deposit guide for that example.
On a repayment mortgage, overpayments can reduce principal earlier and may shorten the term or reduce interest under the model. Real mortgage products can set limits or fees, so check the actual contract.
FREQUENT QUESTIONS
£300,000 mortgage FAQs
What is the monthly payment on a £300,000 mortgage?
There is no single answer. The payment depends on the rate, term, repayment type and the amount actually borrowed after any deposit.
Is a 35-year mortgage cheaper than a 25-year mortgage?
The monthly payment can be lower, but a longer term can increase total interest because the borrowing remains outstanding for longer.
Does the calculator include Stamp Duty?
The mortgage calculator can show an illustrative SDLT amount for the scenarios it supports. Stamp Duty is separate from the mortgage balance and depends on the buyer and transaction.
Run the £300,000 mortgage scenario → · Read how much mortgage you can afford →
Illustrative only. Actual mortgage products can include fees, rate changes and lender-specific terms.
TURN £300,000 INTO A SCENARIO
There is no single monthly cost for a £300,000 mortgage.
The monthly payment depends on how much you borrow, the interest rate and the term. Deposit size also matters because it changes the amount financed. A useful comparison therefore shows the assumptions rather than publishing one universal figure.
£270,000 borrowed
At a fixed 5% rate over 25 years, a standard repayment model is roughly £1,580 a month. Change the rate or term and the payment changes.
Total interest
A mortgage paid over more months can accumulate more interest even when its monthly payment looks lower. Compare the full repayment total, not just the instalment.
Property costs
Mortgage payment is only one housing cost. Allow for insurance, maintenance, service charges where relevant, property tax and household bills.
MoneyHelper describes mortgage calculator results as estimates and notes that lenders consider affordability using income, spending and existing debts. Mortgage repayment guidance → · Mortgage affordability guidance →