A loan and personal-credit calculator that shows your monthly payment, total interest, total cost of credit and representative APR for any fixed-rate, fixed-term loan. Use it to compare personal loans, car finance or HP deals before you apply — especially when arrangement fees make the headline rate misleading.
How it works
The monthly payment is the standard amortising-loan formula:
M = P · r(1+r)ⁿ ⁄ ((1+r)ⁿ − 1)
where P is the amount borrowed plus any financed fees, r is the monthly rate (annual rate ÷ 12 ÷ 100) and n is the term in months. Total repaid is the payment × n. Total interest is total repaid minus the financed amount; total cost of credit is total repaid minus the cash you actually received. When fees are present, the representative APR is found by bisection — solving for the annual rate that ties your repayments to the net cash advanced, which is why it sits above the nominal rate.
Example
Borrow £10,000 at 7.9% over 5 years with no fees:
- Monthly payment: £202
- Total repaid: about £12,120
- Total interest: about £2,120, and the representative APR equals 7.9%.
Add a £300 arrangement fee financed into the loan and the representative APR rises to roughly 9.0%, because you receive £9,700 but repay against £10,300.
| Borrowed | Rate | Term | Monthly payment | Total interest |
|---|---|---|---|---|
| £5,000 | 7.9% | 3y | £156 | £634 |
| £10,000 | 7.9% | 5y | £202 | £2,120 |
| £10,000 | 12.9% | 5y | £227 | £3,620 |
| £20,000 | 5.9% | 7y | £291 | £4,440 |
Why total cost of credit matters more than monthly payment
Lenders promote monthly payments because small figures are less alarming. But the monthly payment hides the total cost of borrowing over the full term. Two loans with the same monthly payment can have very different total costs if their terms differ — a longer term keeps the monthly payment low while accumulating far more interest.
Using this calculator to check total interest and total cost of credit before committing gives you the full picture. As a rule of thumb: every extra year on a loan at a typical rate adds a meaningful amount to your total interest. Shorten the term if you can afford the higher monthly payment; the interest saving is usually worth it.
The arrangement fee effect on APR
Arrangement fees are one of the most common sources of confusion when comparing personal loans. Two loans with the same headline interest rate but different fees have different real costs:
- A loan with no fee: representative APR equals the interest rate.
- A loan with a fee financed into the borrowing: the APR rises because you repay more than you received. The higher the fee relative to the loan amount, the bigger the APR gap.
This means you should always compare loans on representative APR — not headline rate — when fees are involved. The calculator shows both so you can see exactly how much a fee moves the APR on your specific loan size and term.
For guidance only — everything is calculated locally in your browser, nothing is uploaded.