Loan Repayment Calculator
Work out the true cost of a personal or auto loan: monthly payment, total interest, and the full repayment schedule. Add an optional overpayment to see how much faster — and cheaper — the loan becomes.
Optional — see how overpaying shortens the loan
Repayment schedule
| Year | Paid | Interest | Principal | Balance |
|---|---|---|---|---|
| 1 | £3,641.16 | £1,094.09 | £2,547.07 | £12,452.93 |
| 2 | £3,641.16 | £885.42 | £2,755.74 | £9,697.19 |
| 3 | £3,641.16 | £659.66 | £2,981.50 | £6,715.69 |
| 4 | £3,641.16 | £415.41 | £3,225.75 | £3,489.94 |
| 5 | £3,641.07 | £151.13 | £3,489.94 | £0.00 |
How are loan repayments worked out?
Personal and auto loans are amortizing: each fixed monthly payment first covers the month's interest, and the rest reduces the balance. The payment comes from M = P · r(1+r)n / ((1+r)n − 1) with P the amount borrowed, r the monthly rate, and n the number of payments.
Worked example
A £15,000 loan at 7.9% APR over 5 years costs £303.43 a month and £3,206 in total interest. Overpaying just £100 a month clears it 1 year and 5 months early and saves £945 in interest.
Frequently asked questions
How is a loan repayment calculated?
Amortizing loans use the formula M = P × r(1+r)^n / ((1+r)^n − 1), where P is the amount borrowed, r the monthly interest rate (annual rate ÷ 12), and n the number of monthly payments. A $20,000 loan at 7.5% over 5 years costs $400.76 a month.
Does overpaying a loan reduce the interest I pay?
Yes. Extra payments go straight to the balance, so every later month charges interest on a smaller amount. Overpaying shortens the loan and cuts total interest — this calculator shows exactly how many months and how much interest a given overpayment saves.
What is the difference between APR and the interest rate?
The interest rate is the cost of borrowing the money itself; APR (annual percentage rate) also folds in mandatory fees, so it is the better number for comparing offers. This calculator treats the rate you enter as a nominal annual rate charged monthly.
Why is more of my early payment interest?
Interest is charged on the outstanding balance, which is largest at the start. As payments shrink the balance, the interest portion falls and the principal portion grows — the schedule on this page shows the split for every year of the loan.