LOANS & DEBT
Amortization Schedule Calculator
By Worldtickers ·
Use our free amortization schedule calculator to generate a year-by-year breakdown of principal, interest, and remaining balance for any loan — with an optional extra monthly principal payment to see how much faster you could pay it off and how much interest you'd save.
This amortization schedule tool focuses on use our free amortization schedule calculator to generate a year-by-year breakdown of principal, interest, and remaining balance for any loan — with an optional extra monthly principal payment to see how much faster you could pay it off and how much interest you'd save. Use it to test option prices, strikes, premiums, expiration assumptions, and strategy outcomes so you can compare payoff scenarios, break-even levels, risk, and potential reward before placing an options trade.
Amortization Schedule Calculator
Amortization Schedule Calculator
Enter your loan amount, interest rate, and term — add an optional extra monthly principal payment to see how much faster you pay it off. Results include a year-by-year schedule below.
What Is an Amortization Schedule?
Amortization is the process of paying off a loan through regular, fixed payments over time, where each payment covers that period's interest first and applies whatever is left over to principal. An amortization schedule is the detailed record of that process — a table showing, for every payment period, how much went to interest, how much went to principal, and what balance remained afterward.
The shape of an amortization schedule is one of the most counterintuitive things about loans to first-time borrowers: even though your payment is the same every month, the split between interest and principal shifts dramatically over the life of the loan. Early payments are interest-heavy because the balance is largest early on; late payments are almost entirely principal because there's so little balance left to charge interest on.
This calculator builds that full schedule for you and adds one powerful option: an extra monthly principal payment, which shows up as a shorter payoff time and lower total interest in the results. For a calculator focused specifically on comparing mortgage payoff acceleration strategies, see our mortgage payoff calculator.
How to Use This Calculator
Enter your loan details, plus an optional extra payment if you're considering paying ahead of schedule.
Loan Amount
The original principal you borrowed (or your current balance, if you want the schedule going forward from today).
Interest Rate
The annual interest rate on the loan, entered as a percentage.
Loan Term
The full length of the loan in years, as originally agreed (or as it stands, if using a current balance).
Extra Monthly Principal Payment (Optional)
Leave this at $0 to see a standard amortization schedule with no changes, or enter any amount to see how a consistent extra payment every month accelerates your payoff and cuts total interest. The calculator's standard monthly payment (P&I) is always calculated first, based on the loan amount, rate, and term alone — the extra payment is applied on top of that fixed figure.
The Formula Explained
The standard monthly payment uses the amortization formula: M = P × r × (1 + r)^n ÷ [(1 + r)^n − 1], where P is the loan amount, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of scheduled monthly payments. This payment amount is fixed for the life of the loan and does not change even when extra principal is added.
To build the schedule, the calculator then simulates the loan month by month. In each month: Interest = Balance × Monthly Rate. Principal = Standard Payment − Interest + Extra Payment (capped so it never exceeds the remaining balance in the final month). Balance = Balance − Principal. This repeats until the balance reaches zero — which happens exactly at the loan's original term if the extra payment is $0, and sooner than the original term whenever a positive extra payment is entered.
Rather than displaying all of these individual months, the calculator sums each year's 12 months of principal and interest into a single annual row, and records the balance at the end of that year — giving you a compact year-by-year view of the entire schedule, plus overall totals for interest paid and actual payoff time.
Worked Examples
Example 1: $300,000 Loan, 6% Rate, 30-Year Term, $200 Extra Monthly Principal
Standard monthly payment: P = $300,000, r = 6% ÷ 12 = 0.5%, n = 360. M = 300,000 × 0.005 × (1.005)^360 ÷ [(1.005)^360 − 1] ≈ $1,798.65 per month.
With no extra payment, this loan takes the full 360 months (30 years) to pay off and costs $347,514.57 in total interest. Adding $200 extra principal every month, the simulation shows the loan paid off in 279 months — 23 years and 3 months, nearly 7 years early — with total interest of just $256,341.13, a savings of $91,173.44 in interest for an extra $200/month commitment.
The annual summary for this example starts with Year 1: $6,151.15 principal paid, $17,832.67 interest paid, ending balance $293,848.85. By Year 3, the split has already shifted to $6,933.33 principal versus $17,050.49 interest, ending balance $280,384.99 — and by the final (partial) year, only $40.41 of interest remains on a final $4,672.88 principal payment that zeroes out the balance.
Example 2: $150,000 Loan, 5.5% Rate, 15-Year Term, $150 Extra Monthly Principal
Standard monthly payment: P = $150,000, r = 5.5% ÷ 12 ≈ 0.4583%, n = 180. M ≈ $1,225.63 per month. Without extra payments, this loan runs the full 180 months (15 years) and costs $70,612.53 in total interest.
Adding $150 extra principal every month, the loan pays off in 152 months — 12 years and 8 months, more than 2 years early — with total interest of $58,379.19, saving $12,233.34. Notice the interest savings here are proportionally smaller than Example 1's, because a 15-year loan already has less total interest to save from in the first place — extra payments have the biggest dollar impact on longer, higher-rate loans.
Tips and Limitations
Extra Payments Made Earlier Save More
Because interest is calculated on the current balance each month, a dollar of extra principal paid in year 1 removes that dollar from the interest calculation for every remaining month of the loan — far more months than the same dollar paid in year 20 would remove. If you can only afford extra payments some years, front-loading them produces a bigger total interest savings than back-loading them.
Confirm There's No Prepayment Penalty
Most mortgages and personal loans allow extra principal payments freely, but some loans — particularly certain private or subprime loans — charge a fee for paying off early. Check your loan documents before committing to a regular extra-payment plan.
The Annual View Hides Month-to-Month Detail
The annual summary is designed for readability, but if you need a specific month's principal/interest split — for tax purposes or a specific refinancing decision — the same simulation logic used here (run month by month) will produce it; the annual table is simply that same data summed into yearly rows.
Compare Against Investing the Difference
Extra principal payments are a guaranteed, risk-free return equal to your loan's interest rate. Before committing extra cash flow here, compare that guaranteed rate against what you could reasonably expect from investing the same amount instead — see our CAGR calculator to frame that comparison using a historical or assumed investment return.
Frequently Asked Questions
What is an amortization schedule?
An amortization schedule is a breakdown of every payment over the life of a loan, showing how much of each payment goes toward interest versus principal, and what the remaining balance is afterward. Early in the loan, most of each payment is interest because the balance is largest then; later payments are mostly principal because the balance has shrunk. This calculator aggregates that month-by-month detail into an easy-to-read annual summary, rather than listing all 360 (or however many) individual monthly rows.
Why does most of my early payment go to interest?
Interest for any given month is simply your outstanding balance multiplied by the monthly interest rate, and your balance is at its highest right at the start of the loan. Since your total payment is fixed (in a standard, non-extra-payment loan), whatever's left after covering that month's interest goes to principal. As the balance falls month by month, the interest portion shrinks and the principal portion grows, even though your total payment stays the same — this is the defining feature of amortization.
How does extra principal payment affect the schedule?
Every extra dollar you pay goes straight to principal, on top of what your regular payment already covers, which lowers next month's balance and therefore next month's interest charge. That saved interest doesn't just vanish — it effectively becomes more principal reduction on future extra payments too, which compounds over time. The practical result is a loan that pays off earlier than its stated term, with total interest paid meaningfully lower than if you'd made only the standard payment.
Why does the calculator show annual totals instead of every single month?
A 30-year loan has 360 individual monthly rows, which is far more detail than is useful for understanding the shape of your amortization at a glance. Aggregating into annual totals — principal paid, interest paid, and ending balance for each year — makes it easy to see how the mix shifts over time and track your progress year over year, while still capturing everything a monthly table would show, just summed. If you need a specific month's figures, the same formulas used here can be applied to any individual payment number.
Does extra principal payment change my required minimum payment?
No. The extra amount is optional on top of your standard required payment — it isn't a new minimum you have to keep paying every month. You can pay extra one month and skip it the next without penalty on most standard mortgages and installment loans (though always confirm your specific loan doesn't charge a prepayment penalty, which is rare but does exist on some loans).
Will making extra payments always save the same amount of interest?
No — the interest saved from a given extra payment depends on how early in the loan you make it and how large your remaining balance and interest rate are at that point. A dollar of extra principal paid in year 1 of a 30-year mortgage saves far more cumulative interest than the same dollar paid in year 29, because it removes that dollar from the balance for many more months of interest accrual. This is why starting extra payments as early as possible has an outsized effect on total interest paid.
What's the difference between this and a mortgage payoff calculator?
This calculator's core purpose is generating the full year-by-year payment breakdown — principal, interest, and ending balance for every year of the loan — for any type of installment loan, with extra principal as one optional input. A dedicated mortgage payoff calculator is more narrowly focused on comparing payoff strategies specifically for a mortgage, such as bi-weekly payments versus a fixed extra amount. Use this calculator when you want the full schedule; use a payoff calculator when you're specifically comparing payoff acceleration strategies.