Introduction
An amortization calculator helps you see how a loan gets paid off over time. Each month, part of your payment goes toward the amount you borrowed (the principal) and part goes toward interest. This tool breaks down every single payment so you can see exactly where your money goes. Just enter your loan amount, interest rate, and loan term, and the calculator will build a full payment schedule for you. It works for mortgages, car loans, personal loans, and other fixed-rate installment loans that charge interest on the balance you still owe. Use it to compare different loan options, plan your budget, or figure out how extra payments could help you pay off your debt faster and save money on interest.
How to Use Our Amortization Calculator
Enter your loan details below, and this calculator will show you your monthly payment (or maximum loan amount), total interest paid, a full amortization schedule, and helpful charts that break down your loan over time.
Calculation Mode: Choose whether you want to solve for your monthly payment or solve for the maximum loan amount you can afford based on a desired monthly payment.
Loan Amount: Enter the total amount of money you are borrowing. This is the principal balance of your loan before any interest is added.
Annual Interest Rate: Enter the yearly interest rate on your loan as a percentage. For example, if your rate is 6.75%, type "6.75" into this field.
Desired Monthly Payment: If you chose "Solve for Loan Amount" mode, enter the monthly payment you can afford. The calculator will figure out the biggest loan you can take on with that payment.
Loan Term: Enter how long your loan lasts in years and months. You can also click one of the preset buttons (10, 15, 20, 25, or 30 years) to quickly set a common loan term.
Loan Start Date: Select the month and year your loan begins. This sets the starting point for your amortization schedule and payoff date.
Include Extra Payments: Check this box if you plan to make extra payments on your loan. You can add an extra monthly amount, an extra yearly lump sum, or up to 12 one-time payments. The calculator will show you how much interest you save and how much sooner you pay off the loan compared to the original schedule.
Extra Monthly Payment: Enter an additional dollar amount you want to pay each month on top of your regular payment. Set the start date for when these extra payments begin.
Extra Yearly Payment: Enter a lump sum you want to pay once per year, then pick which month and starting year. This is useful for applying a tax refund or bonus to your loan.
One-Time Extra Payments: Click "Add One-Time Payment" to enter a specific dollar amount on a specific date. You can add up to 12 one-time payments to see how large lump sums affect your loan payoff.
Results: After clicking "Calculate," you will see your monthly payment (or loan amount), total of all payments, total interest paid, total principal paid, payoff date, interest-to-principal ratio, and total number of payments. If you included extra payments, a side-by-side comparison shows your original loan next to the accelerated payoff, along with exactly how much interest and time you save.
Charts and Schedule: Scroll down to view a balance-over-time chart, an annual principal vs. interest bar chart, and a total cost breakdown pie chart. The full amortization schedule table can be toggled between a monthly view and a yearly summary view.
What Is Loan Amortization?
Amortization is the process of paying off a loan over time through regular, scheduled payments. Each payment you make is split into two parts: one part goes toward the interest (the cost of borrowing money), and the other part goes toward the principal (the actual amount you borrowed). At the start of a loan, your balance is at its highest, so more of each payment goes toward interest.2 On a 30-year mortgage at 6.75%, for example, about 87% of the first payment is interest. As time goes on, more and more of each payment goes toward paying down the principal. This gradual shift is what an amortization schedule shows you, month by month.
How Amortization Works
When you take out a loan (like a mortgage, car loan, or personal loan), the lender uses a formula to figure out your fixed monthly payment. That formula takes three things into account:
- Loan amount (principal): The total amount of money you borrow.
- Interest rate: The annual percentage the lender charges you for borrowing. This rate is divided by 12 to get the monthly interest rate used in calculations.
- Loan term: How long you have to pay back the loan, usually expressed in years (such as 15 or 30 years for a mortgage).
The standard formula for calculating a monthly payment on a fixed-rate loan is:
M = P × [r(1 + r)n] / [(1 + r)n – 1]2
Where M is the monthly payment, P is the principal, r is the monthly interest rate, and n is the total number of payments. For example, a $250,000 loan at 6.75% interest over 30 years results in a monthly payment of about $1,621. Over the life of that loan, you'd pay roughly $333,700 in interest alone, more than the amount you originally borrowed.
Why the Interest-to-Principal Ratio Matters
The interest-to-principal ratio tells you how much you pay in interest compared to how much you actually borrowed. A ratio of 1.33, for instance, means you paid $1.33 in interest for every $1.00 of principal. A shorter loan term or a lower interest rate will bring this ratio down significantly. This number gives you a quick snapshot of the true cost of your loan beyond just the monthly payment.
The Power of Extra Payments
One of the most effective ways to save money on a loan is by making extra payments. Even small additional amounts applied to the principal each month can make a big difference. Extra payments reduce your remaining balance faster, which means less interest builds up in future months. Each extra dollar you pay saves the interest that dollar would have built up over the rest of the loan, so the earlier you pay it, the more it saves.
There are several ways to make extra payments:
- Extra monthly payments: Adding a fixed amount to your regular payment every month. For example, paying an extra $200 per month from the first payment on a $250,000, 30-year mortgage at 6.75% saves over $100,000 in interest and pays the loan off 8 years sooner.
- Extra yearly payments: Making one larger lump-sum payment each year, such as using a tax refund or bonus.
- One-time payments: Applying a windfall, like an inheritance or savings, directly to your loan balance at a specific point in time.
Before making extra payments, check with your lender to confirm there are no prepayment penalties.1 When you pay more than the amount due, ask your lender or servicer to apply the extra amount to principal.3
Choosing the Right Loan Term
The loan term you choose has a huge impact on both your monthly payment and your total cost. A 30-year mortgage gives you the lowest monthly payment, but you pay the most interest overall. A 15-year mortgage has higher monthly payments, but you save a large amount on interest and build equity in your home much faster. Terms of 20 or 25 years fall in between. A 10-year term has the highest monthly payment and the least total interest of all. The right choice depends on your monthly budget, your financial goals, and how quickly you want to be debt-free.
Tips for Managing Your Loan
- Compare terms before you borrow. Use an amortization schedule to see the total cost of different loan lengths and interest rates side by side.
- Refinance when rates drop. If interest rates fall well below your current rate, refinancing into a new loan can lower your monthly payment, reduce total interest, or both. In many cases you pay closing costs and other fees for the new loan, so check those and any prepayment penalty first.3 A new loan with a longer term can lower your payment but raise the total interest you pay.
- Round up your payments. Even rounding your payment up to the nearest hundred dollars can shave months or years off your loan.
- Review your schedule regularly. Understanding where you are in the amortization process helps you make informed decisions about extra payments or refinancing.
- Account for related costs. Don't forget expenses like closing costs, private mortgage insurance (PMI), and property taxes when budgeting for homeownership.
- Build a financial safety net. Before aggressively paying down your loan, make sure you have an adequate emergency fund.