Amortization Calculator
Generate a full amortization schedule showing principal, interest, and balance for every payment.
| # | Date | Payment | Principal | Interest | Balance |
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Generate a full month-by-month amortization schedule for any fixed-rate loan, showing exactly how much of each payment goes toward principal versus interest and how the balance declines over time.
How Amortization Calculator Works
The monthly payment is calculated with the standard amortization formula: payment = P × [r(1+r)^n] / [(1+r)^n − 1], where P is the loan amount, r is the annual rate divided by 12, and n is the term in years multiplied by 12 (choose from 5 to 30 years).
The schedule is then built one row at a time: each month's interest charge is the current balance times the monthly rate, the principal portion is the payment (plus any extra payment) minus that interest, and the balance is reduced by the principal portion before moving to the next row — continuing until the balance reaches zero.
Because interest is charged on a shrinking balance, the split between interest and principal shifts every month: early payments are mostly interest, later payments are mostly principal. Adding a fixed extra monthly payment directs more toward principal every single month, shortening the schedule and cutting total interest.
See It In Action
Who Uses Amortization Calculator and Why
- Generating a full month-by-month payment breakdown for a mortgage or personal loan to see exactly how the balance declines.
- Understanding why your first year of mortgage payments feels like it barely dents the principal.
- Testing how adding a fixed extra monthly payment reshapes the entire schedule and cuts the number of remaining months.
- Lining up a real payoff schedule against calendar months and years using the start-date field, to match actual loan statements.
Mistakes to Avoid
- Expecting the interest-versus-principal split to stay constant across the loan — it shifts every month as the balance shrinks, so comparing month 1 to month 200 as if they should look similar misses the point of the schedule.
- Changing the start date and expecting it to affect the payment amount — the start date only relabels rows with calendar months, it doesn't change the underlying interest or principal math.
- Overlooking how much a 30-year term inflates total interest — the example shows total interest on a $200,000 loan actually exceeding the original loan amount, which surprises many first-time viewers of a full schedule.
Tips for Best Results
- Look at the full schedule, not just the first month's split, to appreciate how much the principal portion accelerates in the loan's later years.
- If you're deciding whether extra payments are worth it, watch the row count drop rather than just the summary numbers — it makes the time savings feel concrete.
Fixing Common Problems
Almost none of my early payments are reducing the balance. — This is expected behavior for any amortizing loan — interest is charged on the outstanding balance, which is largest early on, so principal reduction accelerates naturally as the balance shrinks over time, not because something is wrong.
Terms Explained
Amortization schedule: A row-by-row breakdown of every loan payment showing the interest charged, principal paid, and remaining balance for each period.
Extra payment: An additional amount added to the required payment each month, applied entirely to principal and reflected across the whole remaining schedule.