Introduction
This free loan interest calculator helps you find out how much interest you will pay on a loan. Enter your loan amount, interest rate, and loan term to see your monthly payment, total interest, and total cost. You can also compare different rates and terms side by side to find the best deal.
The calculator builds a full amortization schedule so you can see how each payment splits between principal and interest. If you plan to make extra payments, you can add those too. The tool will show you how much money and time you save by paying more than the minimum.
Use this calculator for personal loans, auto loans, student loans, or any fixed-rate loan with regular monthly payments. This tool gives you clear numbers to help you make smart choices, whether you are planning a new loan or paying off an existing one faster.
How to Use Our Loan Interest Calculator
Enter your loan details below to find out your monthly payment, total interest, and payoff date. The calculator gives you results right away and shows a full payment schedule.
Choose what to calculate. Pick "Monthly Payment" to find what you owe each month. Pick "Total Interest" to see how much interest you will pay. Pick "Loan Term" to learn how long it takes to pay off your loan.
Enter your loan amount. Type the total amount of money you borrowed or plan to borrow in dollars.
Enter your annual interest rate. Type the yearly interest rate on your loan as a percent. You can find this number on your loan agreement.
Set your loan term. Use the number box or the slider to pick how many months or years you have to repay the loan. You can switch between months and years with the toggle buttons.
Enter your desired monthly payment. This field only shows up if you chose "Loan Term" mode. Type the amount you want to pay each month, and the calculator will tell you how long your loan will take to pay off.
Pick your payment timing. Most loans use "End of Period," which is the standard option. Choose "Start of Period" only if your first payment is due right away.
Add extra payments (optional). Click the extra payments button to open more options. You can add a monthly extra payment, a yearly extra payment, or a one-time extra payment. Enter the amount and the date each one starts. The calculator will show you how much time and money you save.
Click "Calculate." Your results will appear on the right side of the screen. You will see your monthly payment, total interest paid, total amount repaid, and your estimated payoff date. Click "View Full Payment Schedule" to see a month-by-month breakdown of every payment.
What Is Loan Interest?
When you borrow money, the lender charges you a fee for letting you use it. That fee is called interest. It is usually shown as a yearly percentage of the amount you owe. For example, if you borrow $10,000 at a 6% annual interest rate, you pay about $600 in interest during the first year. As you pay down the loan, the interest you owe each month goes down too.
How Loan Interest Is Calculated
Most loans use a method called amortization. Each month, your payment is split into two parts. One part pays the interest. The other part pays down the amount you borrowed, which is called the principal. Early in the loan, most of your payment goes toward interest. Over time, more of it goes toward the principal. By the end, almost all of your payment chips away at the remaining balance.
What Affects How Much Interest You Pay
Three main things decide your total interest cost:
- Loan amount: The more you borrow, the more interest you pay.
- Interest rate: A higher rate means a higher cost. Even a small rate change, like 0.5%, can add up to hundreds or thousands of dollars over the life of a loan.
- Loan term: A longer term means smaller monthly payments, but you pay interest for more months. A shorter term raises your monthly payment but saves you money overall.
How Extra Payments Help
If you pay more than the required amount each month, the extra money goes straight toward your principal. This lowers your balance faster, which means less interest builds up. Even small extra payments made consistently can shave months or years off your loan and save you a significant amount of money.
Payment Timing: End of Period vs. Start of Period
Most loans collect your payment at the end of each month. This is the standard method. Some loans, called annuity due loans, collect payment at the start of each month. When you pay at the start, your balance drops sooner, so you pay slightly less interest overall. Most auto loans, personal loans, and mortgages use end-of-period payments.