Loan and mortgage calculator
Three numbers: how much, what rate, how long. That is the whole of the common question, and it is all this asks for.
Everything else — overpayments, fees, taxes, insurance — is under More options, closed, because most people do not need it and a form that demands it turns them away.
This one runs on your own device. It is worked out in your browser, so there is nothing to send and nothing to log. Where a tool on this site does send something out, that page says so and names where it goes.
The formula, and where your first payment goes
There is one equation behind every mortgage, car loan and personal loan with a fixed rate and a fixed term. It is worth seeing once:
| Symbol | Means |
|---|---|
P | the payment, which is what we are solving for |
A | the amount borrowed |
i | the rate per payment — the annual rate divided by the number of payments a year |
n | the total number of payments |
Then
P = A × i ÷ (1 − (1 + i)−n).
The calculator above prints that line with your own numbers substituted in, so you can check it rather than trust it.
Why the first payment barely touches the debt
Interest is charged on what you still owe, so at the start almost the whole payment is interest and almost none of it is capital. That is not a trick and it is not a fee — it is what “interest on the outstanding balance” means. The reading above splits your first payment in two so you can see it.
It also tells you the month the split crosses over: the point where more of each payment is going on the debt than on the interest. On a long mortgage that can be years in, and it surprises people.
Why this asks for three numbers and not twelve
Most calculators for this ask for the lot up front: price, deposit, term, rate, start date, property tax, insurance, mortgage insurance, service charge, and a few more. Every one of those is a real thing. Only three of them are the question most people arrive with.
A form that demands all twelve before it will tell you anything is a form that works perfectly and sends people away. So the three that answer the question are always visible, the rest are one click away, and the answer appears whether or not you ever open them.
Where to go next
Borrowing and saving are the same arithmetic pointed in opposite directions:
- savings and compound interest calculator — what the same money does if you keep it
- percentage calculator — and the raw sums underneath both
What this does not do
It is arithmetic, not advice. It cannot tell you what you can afford, what rate you will be offered, or whether a deal is good. It assumes a fixed rate for the whole term — if your rate changes, every figure after that point changes with it, and most mortgages in the UK are fixed for a few years and then are not.
Early repayment charges, offset arrangements and interest-only periods are not modelled. Nor is the exact day-count convention your lender uses, which can move the final payment by a few pence.