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Quick Mortgage Calculator: Your Monthly Repayments

Pop in a loan amount, an interest rate and a term. You will see your monthly repayments straight away, what the same loan costs on interest only, and what happens to your payments if the rate goes up by 1%. It's the sum most people want first, so I've put it at the top.

£
%
years

For illustration only and not financial advice. Uses the standard repayment formula and assumes the rate stays the same for the whole term. Real offers depend on the lender, your credit file and fees.

Monthly repayment

£0

Interest only, per month£0
Total repaid over the term£0
Total interest£0
If the rate rose by 1%£0
Full repayment calculator
Borrowing
rate
stamp
Preview of the moving home tool showing example stamp duty and legal costs
Moving Home Calculator

Adds up what moving really costs, from selling fees and any early repayment charge to the deposit left for your next place. Use it before you put your home on the market.

Plan Your Move
Shared Ownership Calculator

Shows the rent, mortgage payment and total monthly cost for the share you buy, and what staircasing later could look like. Use it when you are weighing up a shared ownership home.

Check Affordability
Preview of the shared ownership tool with rent and mortgage figures
Preview of the interest rate comparison tool
Interest Rate Calculator

Compares rates and fees side by side, so you see the true monthly and overall cost of each deal. Use it when your fixed rate is ending or you have two offers to choose between.

Compare Rates
Loan To Value Calculator

Works out your loan to value and the deposit needed for each LTV band. Use it to see whether a slightly bigger deposit could move you into a cheaper rate bracket.

Calculate LTV
Preview of the loan to value tool with an example LTV result
Preview of the borrowing tool showing an income based estimate
Mortgage Borrowing Calculator

Gives you an idea of how much you could borrow based on your income, bonus and monthly commitments. Use it first, before you start booking viewings.

Estimate Borrowing
Overpayment Calculator

Shows how much interest and time you could save by making overpayments, monthly or as a lump sum. Use it when you have spare cash and want to clear your mortgage early.

Calculate Savings
Preview of the overpayment tool showing interest saved
Preview of the stamp duty tool with an example tax figure
Stamp Duty Calculator

Works out how much stamp duty you could pay on a purchase, with separate figures for first time buyers, home movers and additional properties. Use it as soon as you have a price in mind.

Calculate Stamp Duty
Mortgage Repayment Calculator

Shows your monthly repayments and the total cost of the loan over the full term. Use it once you know roughly what you want to borrow and want to test different rates and terms.

Calculate Repayments
Preview of the repayment tool showing a monthly payment
Preview of the offset versus savings comparison tool
Offset Mortgage Vs Savings Calculator

Compares putting your savings into an offset mortgage against leaving them in a savings account. Use it if you hold a decent pot of savings and want to know which works harder for you.

Compare Options
Where to start

Which Mortgage Calculator Do I Need?

Most people only need two or three of these. Here is where I'd point you, depending on where you are in your mortgage journey.

Brick semi detached homes on a Hampshire street, the kind of purchase our mortgage calculators help you plan

Buying your first home

Start with the borrowing calculator to find out how much you could borrow, then the loan to value calculator to see what your deposit gets you. Run the stamp duty calculator on any place you like the look of, because first time buyer relief has a price limit. Looking at shared ownership? The shared ownership calculator shows the rent on the part you don't own. Our first time buyer mortgages guide covers the rest.

Moving home

The moving home calculator is the one to use first. It works out what is left after you sell, clear your mortgage and pay the fees, which is your real deposit. Then check the stamp duty on the new place and run the borrowing calculator again, because your income has probably changed since you last applied. More on porting your deal in our moving home mortgages guide.

Remortgaging

Use the interest rate calculator as your remortgage calculator. Compare a new deal with what you pay now, fees included. A rate that looks cheaper can cost more once a big arrangement fee is added on. If you are an existing customer, your lender will usually offer a product switch, so put that in as one of the options. Our remortgage page explains when moving lender is worth it.

Overpaying

The overpayment calculator shows what making overpayments does to your term and your overall interest. Many lenders let you overpay up to 10% of the balance each year without a charge while you are on a fixed rate, but check your own terms first. If you would rather keep the cash within reach, try the offset mortgage calculator.

Buying to let or investing

These calculators are built for homes you live in. On an investment property the lender looks mainly at the rent, not just your income, and stamp duty includes the higher rate for additional homes. Use the stamp duty calculator for the tax, then speak to us about buy to let mortgages, because rental stress tests vary a lot from one lender to the next.

The maths

How Our Mortgage Calculators Work Out Your Repayments

Repayment mortgages run on one standard formula, and lenders use a version of the same thing. Monthly payment M = P × r × (1 + r)^n ÷ ((1 + r)^n - 1). P is the loan, r is the yearly interest rate divided by 12, and n is the number of monthly payments. In plain English, each month you pay the interest on what you still owe, plus a slice of the loan itself. Early on most of the payment is interest. Later it flips the other way.

Worked example

Take £200,000 over 25 years at 4.5%. That makes r 0.045 ÷ 12, which is 0.00375, and n is 300. Your monthly repayments come out at about £1,111.66, and you'd pay back around £333,500 in total, so roughly £133,500 is interest. On interest only the same loan is £750 a month, but you still owe the full £200,000 at the end.

What a rate change does

Push that rate up to 5.5% and the payment goes to about £1,228.17. That's an extra £116 or so every month from a 1% rate change. Lenders know rates move, which is why they test your affordability at a higher rate than the one you are offered. A longer term brings the payment down, but your overall interest goes up.

Worth knowing

What Mortgage Calculators Can't Tell You

I'm a fan of online mortgage calculators, which is why we built these. But a calculator only knows what you type in. A lender knows a lot more, and this is the bit that trips people up.

Your credit file

No calculator looks at your credit score. Lenders do. Most run a soft credit check at the agreement in principle stage, which other lenders can't see, then a full credit check when you make your mortgage application. A missed phone bill from two years ago could affect which lenders will look at you, so check your file early with our Checkmyfile guide.

Each lender's own rules

Lenders treat income differently. One might count all of your bonus, another half, another none. Self employed income, overtime, maternity leave and childcare costs all get handled their own way. That's why two lenders can give the same couple figures tens of thousands of pounds apart.

Income multiples

Our borrowing calculator shows figures up to 6 times income, because a small number of lenders go that high for some professions and higher earners. Most lenders lend around 4 to 4.5 times income, so treat the top end as a best case, not a promise.

Rates and fees

We don't put live mortgage rates into these tools because they change from week to week. Use a rate you have seen quoted, then speak to us for today's mortgage rates. When you compare a new deal, always add the fees in. Your repayments could look lower while the deal costs more overall.

Why advice still matters

A calculator gives you an idea of how much. An adviser tells you which lender is likely to say yes, at what rate, and what could get in the way. We are fee free on over 90% of the mortgages we arrange, so getting a proper answer usually costs you nothing. Get in touch or call 03300 432 428 for mortgage help from someone who will look at your whole picture.

FAQ

Mortgage Calculator Questions

The questions people ask us most after they have had a go with the calculators.

Are online mortgage calculators accurate?

The maths is accurate. The inputs are the weak point. If the rate, term and loan you enter are right, the monthly repayments figure will be very close to what a lender quotes. What a calculator can't do is tell you whether a lender will accept your application.

Do mortgage calculators affect my credit score?

No. Our calculators don't ask for your name, don't run any credit check and don't store what you type. Your credit file is only searched when a lender runs a check, usually at the agreement in principle or full application stage.

How much could I borrow on my salary?

Most lenders lend around 4 to 4.5 times income, so a £50,000 salary typically means somewhere between £200,000 and £225,000. Some lenders go to 5 or 5.5 times, and a few go higher for certain professions. Car finance, loans and childcare costs bring the figure down.

Which mortgage calculator should a first time buyer use?

Start with the borrowing calculator, then the loan to value calculator to see what your deposit gets you, then the stamp duty calculator. Those three answer the big questions for a first home: how much you can borrow, how much deposit you need and how much tax you pay.

What is the difference between repayment and interest only?

On a repayment mortgage each payment clears some interest and some of the loan, so the balance reaches zero at the end of the term. On interest only you just pay the interest. Payments are lower, but you still owe the whole loan at the end and need a plan to pay it off.

How much does a 1% interest rate change add to my payments?

On a £200,000 repayment mortgage over 25 years, each 1% rise adds roughly £110 to £120 a month for rates between 3.5% and 5.5%. The quick calculator at the top of this page shows what a 1% rise would do to your own figures.

Should I overpay my mortgage or keep the money in savings?

It depends on your mortgage rate, your savings rate and whether you might need the money. Overpaying saves you interest at your mortgage rate. Savings earn the savings rate, less any tax. Keep an emergency fund first, then use the overpayment and offset calculators to compare both.

Are these calculators for UK residents only?

Yes. They are built around UK lending, UK stamp duty and pounds sterling. If you live abroad or are paid in another currency, lenders apply different rules, so speak to us directly instead of relying on the numbers.

Written by Jamie Alexander, Director and Mortgage Adviser (CeMAP) at Alexander Southwell Mortgage Services. Jamie has 15 years in mortgages and founded the firm in 2019. Our team has submitted over 2,500 mortgages, and these calculators use the same sums we run with clients every week. Alexander Southwell Mortgage Services Ltd is authorised and regulated by the Financial Conduct Authority, firm reference 1011890. Last reviewed October 2026.

Want someone to check your figures? Book a free appointment or call 03300 432 428. We are fee free on over 90% of applications. Mortgages under £100,000 carry a £299 fee, and complex or adverse cases can carry a fee of up to £995, which we always confirm in writing before we start.

Our mortgage calculators are for illustration only and are not financial advice. Results depend on the figures you enter and do not mean a lender will offer you a mortgage. Your home may be repossessed if you do not keep up repayments on your mortgage.

Ready to put the numbers into action?

Our calculators give you a useful starting point, but every situation is different. Speak to one of our fee-free advisers to get accurate figures tailored to you. We help clients across Southampton, Romsey and Hampshire with first-time buyer mortgages, remortgages, moving home mortgages and buy-to-let mortgages. You may also want to consider mortgage protection insurance to safeguard your home and finances. Check today's best mortgage rates to see what deals are currently available.