Every loan you repay in fixed monthly installments works the same way: part of each payment covers the interest the lender charges, and part pays down the actual money you borrowed. Amortization is the schedule that splits those two pieces over the life of the loan. This calculator takes your principal, interest rate, and term, then produces your exact monthly payment together with a complete month-by-month amortization table — so you can see how much of each check goes to interest, how much builds equity, and how quickly you actually become debt-free.
Whether it is a car loan, a personal loan, a student loan, or a home mortgage, the math underneath is identical. Adjust the numbers and the schedule rebuilds instantly. Add an optional extra monthly amount to see how much time and interest you would save by paying a little more than the minimum.
How to Use
- Enter the Loan Amount (Principal) — the sum you are borrowing before any interest is added.
- Type your Annual Interest Rate as a percentage. If you do not know it exactly, test a range around your offer, such as ±0.5%, to see how sensitive the payment is.
- Set the Loan Term in years. A longer term lowers the monthly bill but increases total interest; a shorter term raises the bill but costs far less overall.
- Optionally, raise the Extra Monthly Payment slider to model prepayment. Even a modest extra amount toward principal shortens the loan noticeably.
- Read the result card: your Monthly Payment is highlighted, followed by the number of payments, total interest, and the grand total you will repay.
- Scroll to the Amortization Schedule table to inspect any single month — the interest portion, the principal portion, and the remaining balance after that payment.
The table starts almost entirely with interest and steadily shifts toward principal over time. That front-loaded split is the single most important idea in lending, and watching it change as you move the sliders is the fastest way to understand why two loans with the same payment can cost very different amounts.
The Amortization Formula
Your fixed monthly payment comes from the standard formula used by banks, Fannie Mae, and almost every consumer lender:
M = P × r(1 + r)ⁿ / ((1 + r)ⁿ − 1)
Where:
- M is the fixed monthly payment.
- P is the principal, the original loan amount.
- r is the monthly interest rate — the annual rate divided by 12.
- n is the total number of monthly payments — the term in years times 12.
For each month, the lender first charges interest on whatever you still owe. On a $25,000 loan at 6.5% for 5 years, the monthly rate is about 0.005417, n = 60, and the formula produces a payment of $489.15. In month one, interest is roughly $135.42 and principal is about $353.73. In the final month, interest has dwindled to just a few dollars and nearly the entire payment goes to principal. Over the full term, total interest on this loan is about $4,349, bringing the total repaid to roughly $29,349.
If the interest rate is 0%, the formula would divide by zero, so the calculator simply splits the principal evenly across the number of months. A $12,000 interest-free loan over 36 months costs exactly $333.33 per month with no interest at all.
Why the Front Load Matters
At the beginning of an amortizing loan, your balance is at its largest, so the interest portion of each payment is at its largest too. Early on, a large share of your monthly check is rent on borrowed money, not equity. Only later, as the balance shrinks, does the principal portion grow.
This is why refinancing or paying extra early is so powerful: every extra dollar you send in the early months attacks a balance that would otherwise generate interest for years. It is also why selling or refinancing a home in the first few years often yields surprisingly little equity — most of those early mortgage payments went to the lender's interest, not to you.
Examples
Example 1 — A standard personal loan. You borrow $25,000 at 6.5% APR and repay it over 5 years. The calculator shows a monthly payment of $489.15, 60 payments, and total interest of about $4,349. The first payment is split near $135 interest and $354 principal; the last payment is nearly all principal.
Example 2 — An interest-free arrangement. A retailer offers a $12,000 loan at 0% for 3 years. With no interest, the monthly payment is simply $333.33 and total interest is $0.00. Total repaid equals the principal exactly — which is why a true zero-percent deal is such good value.
Example 3 — A large home-style loan. On a $1,000,000 loan at 6.5% over 30 years, the monthly payment is about $6,320.68, but total interest balloons to roughly $1,275,445 — more than the original loan itself. This example shows how dramatically total cost scales with both amount and term, and why refinancing even half a point matters on a jumbo balance.
FAQ
What is amortization in simple terms?
Amortization is the process of paying off a loan with fixed regular payments, where each payment is split between interest and principal. Early payments are mostly interest; later payments are mostly principal. The amortization schedule is the table that shows this split for every month of the loan.
How is my monthly payment calculated?
The payment uses the standard 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 divided by 12), and n is the number of monthly payments. This calculator applies that same formula and then walks balance, interest, and principal forward one month at a time.
What is the difference between amortization and a mortgage?
A mortgage is a specific type of loan used to buy real estate, and it often bundles property tax, insurance, and PMI into the bill. Amortization is the generic repayment schedule that applies to any installment loan — car, personal, student, or mortgage. This calculator models the plain amortization schedule without tax or insurance add-ons.
Does paying extra each month really help?
Yes. Because interest is charged on the remaining balance, every extra dollar toward principal in the early months removes interest that would otherwise compound over future years. Even an extra $50 or $100 per month can cut months or years off the term and save thousands in total interest. Check whether your lender charges a prepayment penalty first.
What happens when the interest rate is 0%?
When the rate is zero, there is no interest to charge, so the calculator divides the principal evenly across the number of monthly payments. Each payment is exactly the principal divided by the number of months, and total interest is zero.
How much of my payment goes to interest at the start?
In the first month, interest is the monthly rate multiplied by the full original balance. On a $25,000 loan at 6.5%, that first-month interest is around $135 on a $489 payment — roughly 28% of the check. That share steadily falls as the balance shrinks.
Disclaimer
This amortization calculator is provided for informational purposes only and does not constitute financial, lending, or tax advice. Results are estimates based on the inputs you enter and the standard amortization formula; actual loan terms, rates, and fees vary by lender, credit profile, and program. Always confirm your exact payment and schedule directly with a licensed lender or financial advisor before committing to any loan.