Loan Calculator

Your monthly repayment is the fixed amount you pay every month until the loan clears. Total interest is what the borrowing costs on top of the amount borrowed, and total paid is the two combined. The split bar shows how much of your payments attacks the debt versus interest. Figures assume a fixed rate for the whole term and exclude arrangement fees, insurance and early-repayment charges — add those when comparing real offers.

Why this one is different

The worked example below is computed by script against the live tool, so the numbers on this page are proven to match what the calculator produces. Fifteen common loan amounts and terms are worked through in full on a linked comparison page, so you can check a scenario close to yours before entering your own.

Where your money goes

The first year of a loan barely dents what you owe

It feels unfair, but it’s just maths: early payments are mostly interest because interest is charged on a big remaining balance. Only later does the balance shrink fast. Seeing this split is the difference between dreading a loan and managing it.

A slightly shorter term or a small regular overpayment attacks the principal directly and can save a surprising amount in total interest — often more than shopping around for a marginally lower rate.

How it works

A fixed-rate loan is repaid in equal monthly instalments over the term. Early payments are mostly interest; later payments are mostly principal. This calculator uses the standard amortisation formula to find the fixed monthly amount that clears the balance exactly by the final payment.

How to use this calculator

Choose your currency.
Enter the loan amount you want to borrow.
Set the annual interest rate and term in years with the sliders.
Read your monthly repayment, plus total interest and total paid, and the principal-vs-interest split.

Watch it in action

A loan of £35,000 at 8.9% over 3 years — entering the amount, dragging the rate and term, and reading the monthly repayment.

Recorded from this page, not a mock-up. The steps below say the same thing in words.

Formula

M = P · r(1+r)ⁿ ÷ ((1+r)ⁿ − 1)

P = loan amount, r = monthly interest rate (annual ÷ 12), n = number of monthly payments.

Example calculation

A £20,000 loan at 6.5% over 5 years:

Monthly payment ≈ £391
Total interest ≈ £3,479
Total paid ≈ £23,479

Frequently asked questions

Does this include fees?＋

No. It calculates repayments on the principal and interest only. Arrangement fees, insurance or early-repayment charges are not included — add them separately when comparing offers.

What is APR vs interest rate?＋

APR bundles the interest rate together with mandatory fees to show the true yearly cost. Use APR to compare loans; use the interest rate here to estimate repayments.

Can I overpay, and how much does it save?＋

An overpayment goes entirely against the principal, so it removes both that amount of debt and all the interest it would have accrued for the rest of the term. Timing matters more than size: the same payment made in year two of a long loan saves far more than it would in the final years. Check your agreement for early repayment charges first.

What happens if I miss a payment?＋

Interest continues to accrue on the outstanding balance, so the total cost rises and the schedule no longer matches this calculation. Most lenders also apply a fee and report the missed payment to credit reference agencies. Contact the lender before missing a payment rather than after.

Why is the total interest so much larger than I expected?＋

Because interest is charged on the outstanding balance every period, and early in the term that balance is nearly the whole loan. On a long term the total interest can approach or exceed the amount borrowed. Shortening the term is the most effective way to reduce it, at the cost of a higher monthly payment.