What are the monthly repayments on a £10,000 loan at 9.9% over 48 months?

A £10,000 loan at 9.9% over 48 months costs £253 a month. Over the term you repay £12,151 in total, of which £2,151 is interest.

Loan repayment calculator

A £10,000 loan at 9.9% over 48 months costs £253 a month. You repay £12,151 in total, of which £2,151 is interest.

What the loan costs in total
Borrowed	£10,000.00
Interest	£2,150.96
Total repaid	£12,150.96

Year	Interest	Capital repaid	Still owing
1	£894.48	£2,143.32	£7,856.68
2	£672.39	£2,365.41	£5,491.27
3	£427.29	£2,610.51	£2,880.76
4	£156.80	£2,880.76	£0.00

How this is worked out

The monthly payment comes from the standard annuity formula: the amount that clears the balance in exactly the term at the given rate. From there the loan is simulated a month at a time rather than solved algebraically, because the interest actually charged depends on rounding the balance to the penny every month and on the final payment being whatever is left rather than a full one. The payment is rounded up rather than to the nearest penny, since a payment rounded down cannot quite clear the loan and leaves a residue stranded in an extra month.

A £10,000 loan at 9.9% over 48 months

The annuity formula gives the payment that clears £10,000 in 48 months at 9.9%.
Month 1: interest of roughly £82 is added to the balance, the payment comes off, and about £171 of capital goes with it.
Each month the balance is smaller, so less of the same payment is interest and more of it is capital.
By month 48 the balance is zero, and the total interest is the sum of every monthly charge along the way.

The same engine drives the mortgage and car finance calculators, and a test checks all three agree with one another to the penny where they overlap.

Why there is nothing to cite here

The rate is the one you were offered, not one anybody publishes, so this calculator cannot go out of date and has no external source to lean on. It shows its method instead.

What catches people out

APR and the interest rate are not the same thing. The APR is designed to include compulsory fees and to be comparable between lenders; the interest rate is just the rate. Entering an APR here gives a slightly conservative answer, which is the safer direction to be wrong in.
The advertised rate is "representative", which means only 51% of successful applicants have to be given it. The rate you are actually offered after a credit check can be considerably higher, and that is the one worth putting in this box.
Interest is front-loaded even though the payment is level. Early payments are mostly interest and late ones mostly capital, which is why settling a loan halfway through does not leave you owing half of what you borrowed.
You have a statutory right to settle early. Under the Consumer Credit Act a lender must accept early settlement and rebate future interest, but may charge up to 58 days of extra interest — so settling saves somewhat less than the remaining interest shown here.
A longer term always costs more in total, at the same rate. Spreading £10,000 over seven years rather than three roughly doubles the interest while making the monthly figure look far more comfortable, which is exactly why longer terms are offered so readily.

Questions

Why does the total repaid exceed what I borrowed by so much?

Because interest is charged every month on whatever is still outstanding, and over a long term that accumulates. The year-by-year table shows the split, and the shape is always the same: interest dominates early, capital dominates late.

Shortening the term is usually the most effective lever. It raises the monthly payment and cuts the total sharply.

Is this the same as an APR calculation?

Close, but not identical. APR is a standardised figure that folds in compulsory fees and assumes a particular timing convention, so a lender quoting 9.9% APR is not charging exactly 9.9% interest on the balance. This page charges the rate you enter, monthly, on what is outstanding.

Entering the APR gives an answer slightly on the cautious side, which is the right direction for a borrowing decision.

What happens if I overpay or settle early?

On most personal loans an overpayment is treated as partial early settlement, and the rules above apply — a rebate of future interest, possibly less up to 58 days of it. That is different from a mortgage, where an overpayment simply reduces the balance and the interest with it.

For mortgages the overpayment calculator models it properly.

Does this work for a car loan?

For an ordinary personal loan used to buy a car, yes. For dealer finance it depends: hire purchase behaves exactly like this, but a PCP defers part of the price to a final balloon payment and works differently. The car finance calculator handles both.