Loan Amortization Calculator
See exactly how every payment splits between principal and interest — month by month, year by year — for any loan.
| Metric | Standard | + Extra | You save |
|---|---|---|---|
| Payoff time | — | — | — |
| Total interest | — | — | — |
| Total paid | — | — | — |
| Month | Payment | Principal | Interest | Balance | Equity |
|---|
Loan amortization is the process of paying off a debt through regular, scheduled payments over time. Each payment covers two things: interest (the cost of borrowing) and principal (the actual debt reduction). Early in the loan, most of your payment goes to interest. Over time, the balance shifts — more goes to principal.
This is why the amortization schedule matters: it shows you exactly how each payment is divided, month by month, so you can see your loan's true cost and find the best payoff strategy.
Disclaimer: This loan amortization calculator is for educational and informational purposes only. Results assume fixed interest rates and equal monthly payments. Actual loan terms, fees, and costs may vary by lender. This is not financial or legal advice. Always review your loan agreement carefully before signing.
How to use this amortization calculator
Enter your loan amount, interest rate, and term. The calculator generates a full amortization schedule — a month-by-month table showing exactly how each payment splits between interest and principal, and how your remaining balance falls over time.
Use this to understand any loan: mortgage, auto, personal loan, or student loan. All you need is the three numbers above.
How to read an amortization schedule
- Payment number — which month in the repayment sequence
- Payment amount — your fixed monthly payment (stays the same throughout for fixed-rate loans)
- Interest portion — the part of your payment covering interest charged that month (highest at the start)
- Principal portion — the part reducing your balance (lowest at the start, grows over time)
- Remaining balance — what you still owe after that payment
Why most of your early payments are mostly interest
Interest is calculated as a percentage of your outstanding balance each month. When the balance is large (early in the loan), a large portion of each payment goes to interest. As the balance shrinks, less interest accrues, so more of each payment chips away at principal — which is why payoff accelerates toward the end.
On a typical 30-year mortgage, you pay more in interest than principal for roughly the first 20 years. This is why making extra principal payments early in a long loan is so impactful — each dollar of principal removed eliminates all the future interest that would have accrued on it.
How to use the schedule to plan extra payments
Look at the interest column for any given month. That is the exact amount you are paying just to service the debt that month — not reducing it. Every extra dollar of principal you pay eliminates that future interest. Even a one-time lump sum payment in year 3 of a 30-year mortgage can save tens of thousands over the life of the loan.
Real amortization examples: where your money actually goes
The numbers below show the first 12 months of a $25,000 personal loan at 8% APR over 5 years (monthly payment: $507). Notice how the interest portion shrinks each month as the balance falls — slowly at first, then faster.
| Month | Payment | Interest | Principal | Balance |
|---|---|---|---|---|
| 1 | $507 | $167 | $340 | $24,660 |
| 2 | $507 | $164 | $343 | $24,317 |
| 6 | $507 | $155 | $352 | $23,217 |
| 12 | $507 | $143 | $364 | $21,367 |
| 30 | $507 | $88 | $419 | $13,099 |
| 60 | $507 | $3 | $504 | $0 |
In month 1, $167 of your $507 payment is pure interest — 33% of the payment does not reduce your balance at all. By month 60, almost the entire payment is principal. Total interest paid over the full 5 years: $3,418. This is the true cost of borrowing $25,000.
How loan term affects total cost: the same loan, very different outcomes
Choosing a longer term lowers your monthly payment but dramatically increases total interest paid. Here is a $30,000 loan at 7% APR across different terms:
| Loan Term | Monthly Payment | Total Interest | Total Cost |
|---|---|---|---|
| 2 years | $1,343 | $2,229 | $32,229 |
| 3 years | $927 | $3,362 | $33,362 |
| 5 years | $594 | $5,640 | $35,640 |
| 7 years | $452 | $7,944 | $37,944 |
Choosing a 7-year term over a 2-year term saves $891/month but costs an extra $5,715 in interest. Whether that trade-off is worth it depends on your cashflow — but most borrowers underestimate the total interest cost when they focus only on the monthly payment.
The compounding effect of extra payments: a concrete example
Extra principal payments work because they reduce the balance on which all future interest is calculated. The earlier you make them, the more interest they eliminate. Here is what different extra payment amounts do to a $200,000 mortgage at 6.5% over 30 years (standard payment: $1,264/month):
| Extra/Month | Payoff Time | Time Saved | Interest Saved |
|---|---|---|---|
| $0 (standard) | 30 years | — | — |
| $100/month | 25 yrs 8 mo | 4 yrs 4 mo | $35,700 |
| $200/month | 22 yrs 9 mo | 7 yrs 3 mo | $58,900 |
| $500/month | 17 yrs 6 mo | 12 yrs 6 mo | $101,400 |
An extra $100/month on a $200,000 mortgage saves over $35,000 in interest and cuts more than 4 years off the loan. The $100 monthly cost over 25 years totals $30,800 — and it saves $35,700 in interest. That is a positive return on the extra payment itself, plus you own your home 4 years sooner.
When negative amortization becomes a risk
Standard amortization reduces your balance with every payment. But some loan structures can cause negative amortization — where your balance actually grows despite making payments — if your payment does not cover the interest charged that month.
This can occur with certain adjustable-rate mortgages (ARMs) with payment caps, income-driven student loan repayment plans where payments are below the accruing interest, and minimum-only credit card payments at high APRs where the required minimum is set very low.
To check whether your payment is covering at least the interest: divide your APR by 12 and multiply by your outstanding balance. That is the monthly interest charge. If your required payment is below this number, your balance is growing, not shrinking. Use the amortization calculator above to verify — if the balance column does not decrease from month 1, your payment is insufficient.
Fixed-rate vs adjustable-rate loans: how amortization differs
This calculator assumes a fixed interest rate — the same rate applies for the entire loan term, and your monthly payment stays constant. Fixed-rate loans are predictable: you can run the full amortization schedule on day one and know exactly what you will pay in month 1 and month 360.
Adjustable-rate loans (ARMs) work differently. They typically start with a fixed-rate period — 3, 5, 7, or 10 years — after which the rate adjusts periodically based on a benchmark index (such as SOFR) plus a margin. After each rate adjustment, the loan is re-amortized: the remaining balance is recalculated over the remaining term at the new rate, producing a new monthly payment.
The implication: with an ARM, you cannot generate a single accurate amortization schedule for the full loan term at origination. You can model the initial fixed period exactly, and you can model scenarios for the adjustable period using the rate caps in your loan documents — typically a periodic cap (how much the rate can change per adjustment) and a lifetime cap (the maximum rate over the life of the loan). Running the worst-case scenario through the amortization calculator tells you the maximum payment you could face after adjustment.
ARMs are not inherently worse than fixed-rate loans — they carry lower initial rates that can produce significant savings if you sell or refinance before the adjustment period begins. The risk is holding an ARM into the adjustable period in a rising-rate environment without a clear exit plan.
When refinancing makes mathematical sense
Refinancing replaces your existing loan with a new one — ideally at a lower rate, a shorter term, or both. The amortization schedule is the right tool for evaluating whether a refinance actually saves money, because it accounts for both the interest savings and the cost of restarting amortization from the beginning.
The break-even calculation: refinancing typically costs 2–5% of the loan amount in closing costs. Divide the total closing cost by the monthly payment reduction to find your break-even month — the point at which the savings offset the cost of refinancing. If your break-even is 28 months and you plan to stay in the home for 10 years, refinancing makes sense. If you plan to sell in 2 years, it does not.
The term reset trap: refinancing a 30-year mortgage in year 8 back into a new 30-year term resets the amortization clock. Even at a lower rate, you may pay more total interest than if you had stayed on your original loan — because you are now paying interest over 38 years instead of 30. Compare the total remaining interest on your current loan against the total interest on the new loan to evaluate the true cost, not just the monthly payment difference.
Refinancing into a shorter term — say, from a 30-year to a 15-year — typically offers a lower rate and dramatically reduces total interest, but increases the monthly payment. The amortization calculator can model both scenarios side by side: enter your remaining balance, the new rate, and each term option to see the exact difference in total interest and monthly payment.
How to Read an Amortization Schedule
An amortization schedule breaks down every payment into its principal and interest components. Early payments are mostly interest — for a 30-year mortgage at 7%, your first payment might be 90% interest. By the final year, almost all of it goes to principal.
Enter your loan amount, interest rate, and term to generate a complete month-by-month schedule. Use the extra payment field to see exactly which month your loan ends early and how much total interest you save.
Why Make Extra Payments?
Extra payments on a loan go entirely toward reducing your principal balance. Because interest is calculated on the remaining principal, a lower balance means less interest charged each month — creating a compounding effect that accelerates payoff.
Even a one-time lump-sum extra payment can meaningfully reduce your total interest. The earlier in the loan you make it, the greater the impact.