Skip to content

Loan calculator

Work out the monthly payment on any fixed-rate loan, see the full interest bill before you sign, and check what one extra payment a month would do to the term. Everything is calculated in your browser.

Loan details

Total
%

A fixed rate is assumed for the whole term. Fees, insurance and early-repayment charges are not included, so treat the result as the arithmetic of the loan rather than the final cost of the deal.

Contractual monthly payment

—

Total interest
—
Total repaid
—
Interest vs. loan
—
Paid off in
—

Balance on the standard payment

Amortisation schedule

PeriodPrincipalInterestBalance

Early payments are mostly interest because interest is charged on the balance you still owe. As the balance falls, the same payment buys you more principal, which is why overpaying early is worth far more than overpaying late.

How the payment is worked out

A fixed-rate loan uses one formula. The monthly payment is the amount that reduces the balance to exactly zero over the term, given the monthly interest rate. Written out, the payment equals the principal multiplied by the monthly rate, divided by one minus (one plus the monthly rate) raised to the power of minus the number of months.

The monthly rate is the annual rate divided by twelve. Every month the lender charges interest on whatever you still owe, and the rest of your payment reduces the balance. That is the whole mechanism, and it is why two loans with the same monthly payment can cost wildly different amounts once the term changes.

Stretching a loan over more years lowers the payment and raises the total interest, sometimes by more than the original amount borrowed. Shortening it does the reverse. Try both in the calculator above before you decide which trade you want.