What is a loan amortization schedule?
A fully amortizing fixed-rate loan is repaid through repeated payments. Each payment covers interest on the remaining balance, and the rest reduces the principal. As the balance declines, the interest share falls while the principal share grows.
Fixed monthly payment formula
For principal P, monthly interest rate r, and number of monthly payments n:
Payment = P × r ÷ [1 − (1 + r)^(-n)]
Use r = annual interest rate ÷ 1200 when APR is entered as a percentage, and n = loan years × 12. At 0% APR, the monthly payment is simply P ÷ n.
A standard loan example
A $200,000 loan over 30 years at 6% has a scheduled principal-and-interest payment of approximately $1,199.10 per month. The first month’s interest is $1,000, so only about $199.10 pays down principal. Later payments devote a larger share to principal.
Why extra principal payments matter
The calculator keeps the scheduled payment visible and allows an extra monthly principal payment. Extra payments are applied after interest, and the last payment is limited to the remaining amount owed. This can shorten the modeled payoff term significantly.
How to interpret the schedule
The first 12 scheduled rows show month number, amount paid, interest portion and remaining balance. Total paid includes both principal and interest. This calculator uses a monthly periodic model, not daily-interest accrual.
Costs it does not model
Insurance, mortgage property taxes, private mortgage insurance, closing costs, prepayment charges, rate changes and lender fees are excluded. Check actual lender statements when comparing refinancing or early payoff decisions.
Important calculation assumptions
The entered term is rounded to a whole number of months. Interest is computed using the remaining balance and monthly rate; calculations carry full precision and display money to cents. The 0% case is handled separately to avoid dividing by zero.
Learn the schedule in detail
Our loan amortization walkthrough explains why the interest and principal shares evolve even while the scheduled payment stays the same.