Know the numbers before anyone quotes them.
Five calculators that share their figures, so you type things once. Built by a qualified mortgage & protection adviser, and honest about the parts that actually cost people money — the fees, and the rate your deal falls onto when the fix ends.
The monthly payment, what the fees really add, and what happens to it when your deal ends.
The honest headline range lenders start from, before they look at your outgoings.
What an extra £50 a month, or a lump sum, actually buys you.
Compare two deals properly — including fees, and any charge for leaving early.
Savings sitting against your mortgage instead of earning interest. See what they are worth.
Rental yield, and the rent-cover test that really decides what a buy-to-let lender will lend.
Purchase taxes: go to the source
Stamp duty and transfer fees are not calculated here on purpose — the rates move with government budgets. These are the authorities who publish the current ones.
- England & Northern Ireland — Stamp Duty Land Tax: HMRC’s own calculator (opens in a new tab)
- Scotland — Land & Buildings Transaction Tax: Revenue Scotland (opens in a new tab)
- Wales — Land Transaction Tax: GOV.WALES (opens in a new tab)
- Cyprus — property transfer fees: Department of Lands & Surveys (opens in a new tab)
- Cyprus — stamp duty on the contract, and VAT on new builds: Tax Department (opens in a new tab)
Estimates, not an offer. These tools do exactly what you tell them, using standard mortgage arithmetic. A lender applies its own affordability rules, its own fees and its own view of your circumstances, and may reach a different answer. Nothing here is financial advice or a recommendation of any particular product.
Worth knowing before you commit
What is a reversion rate, and why does it matter so much?
It is the rate your mortgage falls onto when your fixed or tracker deal ends — usually the lender’s standard variable rate, and usually a good deal higher. Most people focus on the initial rate and get a shock two or five years later. These tools show both, and what you will still owe at the point it changes.
Why does a lower interest rate sometimes cost more?
The product fee. A lower rate with a £1,999 fee can easily cost more over a two-year fix than a slightly higher rate with no fee, because the saved interest never catches up with the fee. "Should I switch?" compares the true cost of both, fees included, which is the only comparison that means anything.
Should I overpay to reduce the term or reduce the payment?
They are different things and most lenders offer both. Reducing the term keeps your payment the same and finishes the mortgage sooner, which saves far more interest. Reducing the payment keeps the end date and lowers what you pay each month, which helps cash flow now. The overpayment tool shows both, so you can see the trade rather than guess at it.
How accurate is this?
The arithmetic is exact and automatically tested: payments, balances and totals reconcile to the penny, and the tests run every time the site is built. What it cannot know is your lender’s own rules — their affordability model, their fees, their stress rate, and what they make of your circumstances. Treat every figure as a well-informed estimate, not an offer.
What about stamp duty and transfer fees?
These tools deliberately do not calculate them. The rates change with government budgets, they are different in England, Scotland and Wales, and different again in Cyprus — a figure that quietly goes out of date would be worse than no figure at all. Use the official calculators instead, linked just below, and treat the purchase tax as a separate line in your budget alongside your deposit and legal fees.
Does anything I type get sent anywhere?
No. Every calculation runs in your browser. Nothing is stored, nothing is transmitted, there is no sign-up and no cookie for this. Close the tab and it is gone.
Talk it through with someone who does this properly
A calculator cannot tell you which lender will say yes, or what a broker would spot in your circumstances. A conversation can. The first fifteen minutes are free.