Loan Calculator

See the monthly repayment, what the loan costs in total, and where every instalment goes.

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What this tool does

Loan Calculator treats your figures as a fixed-rate, monthly-rest repayment loan. It divides the annual rate by twelve, solves the standard annuity formula for the level payment that clears the balance over the agreed term, then walks the schedule month by month, splitting each instalment into interest charged on the outstanding balance and principal taken off it. A rate of zero is accepted and simply spreads the amount evenly across the term.

The summary gives the monthly payment, the total repaid, the total interest and the share of everything you hand over that is interest rather than debt — the last of those is usually the figure that changes minds. Underneath it you can show yearly totals, every individual month, or nothing beyond the summary. Enter an extra monthly repayment and the schedule is recalculated alongside the original one, so the page can say how much sooner the loan clears, in years and months, and how much interest that avoids.

What it does not model is worth knowing before you lean on a number. The rate is fixed for the whole term: no tracker, no fixed period that reverts to a standard rate, no change halfway through. Arrangement fees, insurance, taxes and early-repayment charges are not in the total. The extra repayment is a constant amount paid every month from the first instalment rather than a lump sum dropped in later. And the amounts carry no currency symbol, because the tool never asks which currency you meant — enter pounds and you are reading pounds.

Everything is computed in this browser tab, so the amount, the rate and the term you type stay in the page and are not sent anywhere. Expect a small difference from a real offer even so: the payment here is rounded to the cent with the final instalment absorbing the drift, which is how lenders do it, but individual lenders accrue interest daily or on their own day-count basis, and some markets quote a rate compounded semi-annually rather than monthly.

How to use it

  1. Enter the amount, rate and term. Four number fields: the loan amount, the annual interest rate as a percentage, the term in years, and any extra monthly repayment. They start at 250,000 at 5.5% over 25 years, which is there to be overwritten.
  2. Or type the figures instead. The input box is optional. Lines such as amount: 180000, rate: 4.2, term: 20 and overpayment: 150 override the fields, so a scenario can be kept as text and pasted back later. A field name it does not recognise is rejected by name rather than quietly ignored, and a fractional term is rounded to the nearest whole month.
  3. Choose how much of the schedule to show. Yearly totals for a readable overview, Every month for the complete amortisation table, or Summary only when the payment and the interest are all you came for.
  4. Read the split, not just the payment. Each row shows the amount paid, how much of it was interest, how much came off the balance, and what is still owed at the end of that period. Early rows are mostly interest; that is the point of looking.

Processing & privacy

Runs on your device. Your file is processed directly in this browser.

Common use cases

Comparing two mortgage offers

Run the same amount and term at each rate. The gap in total interest is usually far wider than the gap in monthly payment makes it look.

Deciding whether to overpay

Put the amount you could spare into the extra repayment field. The months saved and the interest avoided are the two numbers that actually settle the question.

Choosing between a short and a long term

The same car loan over three years and over five shows exactly what the smaller monthly payment costs across the whole agreement.

Sanity-checking a quoted figure

If a broker's monthly number sits well above this one, the difference is normally fees, insurance or a different compounding basis rather than arithmetic — and now you know roughly how much of it to ask about.

Questions

Are my figures sent anywhere?
No. The calculation is JavaScript running in this tab, so the amount, rate and term never leave the page. There is no account and nothing on a server to delete afterwards; the one thing kept locally is this tool's name in the browser's recently-used list, which records that you opened the page and none of the numbers you typed into it.
Why are the amounts shown without a currency symbol?
Because nothing on the page asks which currency you meant. The figures are grouped and pointed the way your browser formats numbers, then left unlabelled, so what you typed in is what you are reading out. A symbol in front of a typed figure is stripped before the number is parsed, which is why amount: £180,000 is read as 180000.
Why is my lender's payment slightly different?
Rounding and convention. This is the annuity payment rounded to the cent, with the last instalment absorbing the leftover fraction. Lenders add fees to the balance, may accrue interest daily, sometimes compound on a different basis, and round in their own direction.
Can it do interest-only, or a balloon payment at the end?
No. Every schedule is a repayment loan that reaches a zero balance by the last instalment. Interest-only periods, payment holidays, offset accounts and final lump sums are outside what this models.
Can I add a one-off overpayment?
Not directly — the extra repayment is a fixed amount applied every month from the start. To approximate a lump sum paid at the outset, subtract it from the loan amount and run the figures again.
What happens if I enter a very high rate?
Over a long term at a punishing rate, the level payment rounded to the cent can be swallowed whole by that month's interest, leaving nothing to come off the balance. Rather than build a schedule that never reaches zero, the tool stops and says so, quoting the rate it was given. A rate above 1,000% a year, a term beyond 100 years, or a term that works out shorter than a single month is refused before any schedule is attempted.
Is this financial advice?
No. It is arithmetic on the numbers you supply. Whether a loan is affordable, how much rate risk you are taking and whether it suits you at all are questions for a qualified adviser and for the lender's own illustration.

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