Enter how much you want to borrow, the annual interest rate and the term. The calculator shows your monthly repayment, the total interest and the total you will pay back.
Results are estimates for planning. Check the figures before you make a financial or health decision.
How the Loan repayment works
The calculator uses the standard repayment formula. With a monthly rate r (the annual rate divided by 12, as a decimal) and n monthly payments (years × 12), the payment is:
P × r ÷ (1 − (1 + r)^−n)
where P is the amount borrowed. If the rate is 0%, it simply divides the amount by the number of payments. Total repaid is the payment multiplied by n, and total interest is that figure minus what you borrowed.
- Each payment covers that month’s interest first, and the rest reduces the balance, so interest falls over time.
- It assumes one fixed rate for the whole term and equal monthly payments.
- Arrangement fees, insurance, early repayment charges and rate changes are not included.
- The rate you enter should be the interest rate, not the APR, unless you want fees reflected roughly.
This also works for a repayment mortgage, though a mortgage rate often changes after an initial deal.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Amount borrowed | £250000 |
| Annual interest rate | 4.5 % |
| Term | 25 years |
Monthly repayment: £1,389.58
| Amount borrowed | £250,000.00 |
|---|---|
| Total interest | £166,874.36 |
| Total repaid | £416,874.36 |
| Number of payments | 300 |
Tips and common mistakes
Try several terms. A longer term lowers the monthly payment but usually raises the total interest by a large amount, so compare both numbers. Check whether the lender’s quote includes fees, and compare loans using the APR as well as the monthly cost. See what happens if you overpay: paying extra early shortens the term and cuts interest, though some loans charge for it. Make sure the repayment fits your budget with room to spare. This is general information, not financial advice.
Frequently asked questions
How is the monthly loan repayment worked out?
It uses the formula P × r ÷ (1 − (1 + r)^−n), where r is the monthly interest rate and n is the number of monthly payments. Each payment is the same size for the whole term.
Does this include fees or the APR?
No. It uses the interest rate you type in and ignores arrangement fees, insurance and charges. The APR on a quote is designed to include some of these, so use it to compare offers.
Can I use it for a mortgage?
Yes, for a repayment mortgage on a single fixed rate. Many mortgages change rate after an initial period, so treat the result as an estimate.