The core formula
Each reducing-balance payment first covers interest on outstanding principal; the rest reduces the balance. Early installments typically contain more interest. An amortization schedule makes that split explicit and helps verify the final balance and interest total.
Worked example
A $1,000,000 loan at 4% for 25 years is about $5,278/month on a standard monthly reducing balance.
How a reducing-balance payment is calculated
- Start with the financed principal after any down payment.
- Convert the annual nominal rate to the rate for each payment period.
- Convert the term into the total number of payments.
- Apply the amortizing-payment formula. Each payment includes interest on the outstanding balance plus principal repayment.
What the monthly payment leaves out
A standard amortization payment covers principal and interest under the assumed rate and term. Fees, insurance, taxes, early-settlement charges or variable-rate changes may sit outside that figure unless they are added explicitly.
Early payments contain more interest because the outstanding principal is larger. As the balance falls, a greater share of each scheduled payment goes toward principal.
Common mistakes
- Using the annual percentage rate directly as the monthly rate.
- Comparing a flat-rate quote with a reducing-balance rate as if they were the same calculation.
- Ignoring mandatory fees when comparing the total cost of two loans.
Use the calculator
Calculate loan payments, total interest, principal, fees, APR and a complete amortization schedule.
Open Loan Payment & Amortization CalculatorUnderstand the payment schedule rather than the headline installment
Each reducing-balance payment first covers interest on outstanding principal; the rest reduces the balance. Early installments typically contain more interest. An amortization schedule makes that split explicit and helps verify the final balance and interest total.
Flat rate and reducing-balance rate are not interchangeable
A flat annual rate is applied to original principal for the quoted duration, while reducing-balance interest is charged on principal remaining. Equal numerical rates can represent very different borrowing costs. Bank fees, payment frequency and timing can also change the effective annual cost.
Frequently asked questions
Why is the interest portion higher at the start?
Interest is charged on the outstanding balance, which is largest at the beginning of an amortizing loan.
Is APR the same as the interest rate?
Not necessarily. APR can include certain fees and is designed as a broader annualized cost measure.
Does the calculator include early repayment?
A standard payment calculation assumes the scheduled term. Extra payments require a revised amortization schedule.
What should I verify about flat rate and reducing-balance rate are not interchangeable?
A flat annual rate is applied to original principal for the quoted duration, while reducing-balance interest is charged on principal remaining. Equal numerical rates can represent very different borrowing costs. Bank fees, payment frequency and timing can also change the effective annual cost.