π Loan Amortization Calculator
Monthly payment, total interest, and the full month-by-month schedule.
Monthly Payment
Estimates for planning only, not financial advice.
How to Use This Calculator
Enter any loan amount, rate, and term to see the monthly payment, the total interest, and the payoff date, followed by the complete amortization schedule. It works for auto loans, personal loans, student loans, and mortgages: any loan paid back in fixed installments.
Enter the Loan Amount (what you actually borrow, after any down payment) and the APR as a yearly percentage.
Enter the Term in years. Fractions work too, so a 42-month car loan is 3.5 years.
Optionally enter Extra Principal per month to see how much interest it saves and how much earlier you pay off the loan.
Scroll through the schedule, switch to the Yearly summary view, or download the full table as CSV.
The Amortization Formula
Every fixed payment is made of two pieces. Interest is always charged on the current balance, so it is biggest in month one. Principal is whatever is left of the payment, so it grows every month as the balance falls. The formula simply finds the one payment amount that makes the balance hit exactly zero at month n. The same math powers mortgages, car loans, and personal loans; only the term and rate change.
Worked Example
$25,000 loan at 6 percent APR for 5 years (60 months). Monthly rate r = 0.06/12 = 0.005. Payment = 25000 x 0.005 x (1.005)^60 / ((1.005)^60 - 1) = $483.32. Total paid = 483.32 x 60 = $28,999.20, so total interest = $3,999.20. Month 1: $125.00 interest, $358.32 principal. Month 60: $2.40 interest, $480.92 principal. Same payment, totally different split, which is the essence of amortization.
Reading Your Schedule Like a Lender
Two things in the schedule matter most. First, the crossover point where principal finally exceeds interest in a single payment: before it, the loan feels slow; after it, the balance drops fast. Second, the total interest row: it tells you the true price of borrowing. Shortening the term or adding extra payments attacks that number directly. A useful rule of thumb is that doubling the principal portion of your early payments, through extra payments, cuts the total interest far more than any rate negotiation of a quarter point.
Estimates for planning only, not financial advice.
Frequently Asked Questions
What is amortization?
Amortization is the process of paying off a loan in fixed monthly installments. Each payment is split between interest (charged on the remaining balance) and principal (which reduces the balance). Because the payment stays the same while the balance shrinks, the interest portion falls and the principal portion grows with every month.
Why do early payments go mostly to interest?
Interest is charged each month on the current balance, and the balance is highest at the start. On a $25,000, 6 percent, 5-year loan, the first $483.32 payment is $125 of interest and only $358.32 of principal. By the last year, the same payment is almost entirely principal. This is normal for every amortizing loan, not a penalty.
How do extra payments change the schedule?
Any extra amount goes directly to principal, so the balance falls faster and every later payment carries less interest. An extra $100 a month on a $25,000, 6 percent, 5-year loan pays it off about a year early and saves over $600 in interest. The effect is largest in the early years when interest dominates.
What does the payoff date mean?
The payoff date is when the balance reaches zero at your current payment schedule, assuming the rate stays fixed and you never miss a payment. It is the last month of the amortization schedule. If you make extra payments, the payoff date moves earlier; if you defer payments or the rate adjusts upward, it moves later.
How does a fixed vs variable rate affect amortization?
With a fixed rate, the payment and schedule never change, so this calculator's table is exact. With a variable rate, every rate change recalculates the payment for the remaining term, so the schedule is only valid until the next adjustment. Variable-rate borrowers can still use this tool by entering the current rate and remaining term to see the picture as of today.