Amortization Calculator
Build a full amortization schedule for any loan — yearly and payment-by-payment principal, interest and balance, with payment dates, extra payments, biweekly options and charts.
How it works
Payment M = P × i ÷ (1 − (1 + i)^−n) · each period: interest = balance × i, principal = M − interest (+ any extra), new balance = balance − principal
P is the amount borrowed, i the interest rate per payment (the annual rate ÷ 12 for monthly payments) and n the number of payments. The payment stays the same, but its split changes every period: interest is charged on the remaining balance, which is largest at the start, so early payments are mostly interest and later ones are mostly principal. The schedule repeats that step for every payment and lists it payment by payment and summed by loan year, with dates from your first payment date. The crossover point is the first payment in which more goes to principal than to interest. Extra payments — with every payment, once a year or one-time amounts — go straight to principal, so the balance falls faster, the loan ends early and less interest builds up; the savings are measured against the same loan without extras. For biweekly, weekly or quarterly payments the rate is converted to that period, and the compounding option covers loans quoted with daily, semi-annual (Canadian) or effective annual rates.
Worked example
A $250,000 loan at 6% for 30 years: i = 0.06 ÷ 12 = 0.005 and n = 360, so M = 250,000 × 0.005 ÷ (1 − 1.005^−360) = $1,498.88. Payment 1 is $1,250.00 of interest and $248.88 of principal. In year 1 you pay $14,916 of interest and $3,070 of principal, leaving $246,930. Principal first exceeds interest at payment 223, after more than 18 years. Total interest is about $289,595. Adding $100 to every payment pays the loan off in 25 years 6 months and saves about $51,600 of interest.
Sources: CFPB — What is amortization and how could it affect my auto loan?
Frequently asked questions
Why does the first year pay so little principal?
Interest is charged on the outstanding balance, which is at its maximum at the start. The fixed payment only has what is left after interest to reduce the balance. The “principal exceeds interest from” result shows when that flips.
How do extra payments change the schedule?
Turn on extra payments to add an amount to every payment, a yearly lump sum or up to two one-time payments. Each extra dollar comes straight off the balance, so every later payment has less interest in it. The schedule gains an Extra column, the chart shows the balance with and without extras, and the results show the interest saved and how much sooner the loan ends.
What does one extra payment a year do?
On the default $250,000 loan at 6% for 30 years, one extra $1,498.88 payment a year (entered as a yearly extra) pays the loan off in about 24 years 9 months and saves about $59,100 of interest, as long as your lender applies it to principal.
Can I see the remaining balance at a given point?
Yes. The yearly schedule shows the balance at the end of every loan year and the payment schedule shows it after every payment. Under More options you can also pick a year to show as a separate result, which helps if you plan to sell, refinance or pay the loan off early.
Is this the same for car and personal loans?
Yes — any fixed-rate amortizing loan follows this schedule, just with smaller numbers and shorter terms. Use the Plus months field for terms such as 4 years 6 months, and the payment frequency for loans paid weekly or every two weeks.
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This is an educational estimate, not financial advice. Lenders use their own rounding, fees and credit terms — confirm exact figures with your lender or a licensed advisor.