An amortization schedule shows how every loan payment is split between interest and principal. Enter the loan amount, the yearly interest rate and the loan term in years. If you plan to pay extra each month, add that amount in the last box, and the schedule will adjust to show the faster payoff.
After you press Calculate, you will see your regular monthly payment, how the very first payment is divided, the total interest, the total you will repay and the time it takes to finish the loan. Below that is a year by year table. For each year it lists the principal paid, the interest paid and the balance still owed at the end of that year.
Look at the first few rows and then the last few. Early on, most of each payment goes to interest. Near the end, most of it goes to principal. This is why extra payments made early in a loan save the most money. The table scrolls on small screens, so you can read it comfortably on a phone.
The regular payment is: payment = loan x r / (1 – (1 + r) raised to minus n), where r is the yearly rate divided by 1200 and n is the number of months.
The schedule is built one month at a time. Interest for the month is the balance times r. The principal part is the payment minus that interest. The new balance is the old balance minus the principal part. Any extra payment goes straight to principal, so the balance falls faster and the loan ends sooner. The yearly rows add up twelve months of principal and interest.