Finance calculators

Installment Calculator

Updated Jul 17, 2026 By Jehan Wadia
Rate Formulas
Loan Details
Enter an amount from $0 to $9,999,999.
Range 0% to 25%.
3 months360 months (30 years)
Payment Timing End of period: you pay at the end of each month (standard). Start of period: you pay at the beginning of each month, which slightly reduces total interest.

Results Summary
$0.00
per month

Loan summary statistics
Monthly Payment The fixed amount paid each period toward principal and interest.
Total Number of Payments
Total Principal Paid The original amount you borrowed.
Total Interest Paid The total cost of borrowing, on top of the principal, over the life of the loan.
Total Amount Paid
Payoff Date The calendar month and year the final payment is made, based on today's date.
Principal vs. Interest
Principal Interest
Principal vs. Interest Breakdown
Interest Rate Sensitivity
How monthly payment and interest change with different rates
Interest RateMonthly PaymentTotal InterestTotal Paid
Step-by-Step Solution
Amortization Schedule
Amortization schedule

Introduction

This free installment calculator helps you figure out the monthly payment on a loan. Just enter the loan amount, interest rate, and loan term, and the tool does the math for you. It shows how much you will pay each month, how much interest you will owe over time, and when your loan will be fully paid off.

You can also use this calculator the other way around. If you already know how much you can pay each month, it will tell you how long it will take to pay off your loan. The built-in amortization schedule breaks down every single payment so you can see exactly how much goes to principal and how much goes to interest.

Need to pay off your loan faster? Use the extra payments feature to see how adding even a small amount each month can save you money on interest and shorten your loan term. You can also compare two different loan options side by side to find the best deal before you borrow.

How to Use Our Installment Calculator

Enter your loan details below to find out your monthly payment, total interest, and full payoff schedule. The calculator gives you a complete breakdown of every payment from start to finish.

Choose what to solve for. Click "Fixed Term" if you know how long the loan is and want to find your monthly payment. Click "Fixed Payments" if you know how much you can pay each month and want to find how long the loan will take to pay off.

Loan Amount. Type in the total amount of money you are borrowing. This can be any value from $1 up to $9,999,999.

Annual Interest Rate. Enter the yearly interest rate your lender charges. This must be between 0% and 25%. The calculator splits this into a monthly rate for you. If you need help determining your rate, try our interest rate calculator.

Loan Term. If you chose "Fixed Term," type in how long the loan lasts in years or months. You can also drag the slider to pick a length between 3 and 360 months. The years and months fields stay in sync.

Monthly Payment. If you chose "Fixed Payments," type in the amount you plan to pay each month. This must be high enough to cover at least the first month's interest, or the loan will never be paid off.

Payment Timing. Pick when each payment is made. "End of Period" means you pay at the end of each month, which is the standard for most loans. "Start of Period" means you pay at the beginning, which lowers your total interest slightly.

Extra Payments (optional). Click this section to open it. You can add an extra amount to your payment each month, a lump sum once per year, or a single one-time payment. For each option, enter the dollar amount and choose the month and year it starts. These extra payments help you pay off the loan faster and save on interest. For a deeper look at how extra payments impact your loan, see our dedicated early payoff calculator.

Calculate. Press the "Calculate" button to see your results. You will get your monthly payment amount, total interest paid, total cost, payoff date, a principal-vs-interest chart, a rate comparison table, a step-by-step math solution, and a full amortization schedule.

Compare Scenarios. Press the "Compare Scenarios" button to see two loans side by side. Change the loan amount, rate, or term for each scenario to see how they differ in monthly payment, total interest, and payoff date.

Reset. Press the "Reset" button to clear all your inputs and start over with the default values.

What Is an Installment Loan?

An installment loan is money you borrow and pay back in equal monthly payments over a set period of time. Each payment you make covers two things: part of the original amount you borrowed (called the principal) and a fee the lender charges you for borrowing (called interest). Common examples include car loans, personal loans, and student loans.

How Installment Payments Work

When you first start paying, most of your monthly payment goes toward interest. As time goes on, more of your payment goes toward the principal. This shift happens because interest is calculated on the remaining balance, which gets smaller with every payment you make. By the end of the loan, almost all of your payment goes toward paying down what you owe. This process is known as amortization, and you can explore it in detail with our amortization calculator.

How This Installment Calculator Helps

This calculator lets you figure out your loan in two ways. First, you can enter a loan amount, interest rate, and loan term to find out your monthly payment. Second, you can enter a loan amount, interest rate, and a monthly payment you can afford to find out how long it will take to pay off the loan. It also shows you a full payment schedule so you can see exactly how each payment is split between principal and interest. For a broader look at any type of borrowing, you can also try our general loan calculator.

Extra Payments Can Save You Money

Paying even a little extra each month can make a big difference. Extra payments go straight toward your principal, which lowers your balance faster. A lower balance means less interest builds up. This can help you pay off your loan sooner and spend less money overall. The calculator lets you add monthly, yearly, or one-time extra payments so you can see how much time and money you could save. If you are juggling multiple debts and want a strategy to pay them all down, check out our debt snowball calculator or debt avalanche calculator.

Key Terms to Know

  • Principal – The original amount of money you borrow.
  • Interest Rate – The yearly percentage the lender charges you for borrowing. It is divided by 12 to get the monthly rate. To understand the true cost of borrowing including fees, use an APR calculator.
  • Loan Term – The total length of time you have to pay back the loan.
  • Amortization Schedule – A table that shows every payment broken down into principal, interest, and remaining balance.
  • Annuity Due – When you make your payment at the start of each month instead of the end. This slightly lowers the total interest you pay. For more on annuity math, see our annuity calculator.

Formulas used

Monthly Interest Rate
i = \dfrac{r}{12}
Monthly Payment (Ordinary Annuity — End of Period)
PMT = \dfrac{P \cdot i}{1 - (1 + i)^{-n}}
Monthly Payment (Annuity Due — Start of Period)
PMT = \dfrac{P \cdot i}{\left(1 - (1 + i)^{-n}\right)(1 + i)}
Number of Payments (Solve for Loan Term)
n = \dfrac{-\ln\!\left(1 - \dfrac{P \cdot i}{M}\right)}{\ln(1 + i)}
Total Interest Paid
\text{Total Interest} = \text{Total Paid} - P

Frequently asked questions

What is the formula used to calculate the monthly payment?

The calculator uses the standard installment formula: PMT = (P × i) ÷ (1 − (1 + i)^−n), where P is the loan amount, i is the monthly interest rate (annual rate ÷ 12), and n is the total number of monthly payments. If you choose "Start of Period" timing, the result is divided by (1 + i) to account for paying at the beginning of each month.

What is the difference between Fixed Term and Fixed Payments mode?

Fixed Term means you enter the loan length and the calculator finds your monthly payment. Fixed Payments means you enter how much you can pay each month and the calculator finds how many months it will take to pay off the loan. Use Fixed Term when you know the loan length. Use Fixed Payments when you have a set budget.

Why does my payment need to be higher than the first month's interest?

If your monthly payment is less than or equal to the interest charged in the first month, your balance never goes down. It stays the same or grows larger. The loan would never be paid off. Your payment must be big enough to cover the interest and still leave some money to reduce the principal.

What does End of Period vs Start of Period mean?

End of Period means you pay at the end of each month. This is how most loans work. Start of Period (also called annuity due) means you pay at the beginning of each month. Paying at the start gives interest less time to build up, so you pay slightly less total interest over the life of the loan.

Why does most of my early payment go to interest?

Interest is charged on your remaining balance. At the start of a loan, your balance is at its highest, so the interest charge is large. As you make payments and the balance drops, less interest builds up each month. This means more of each payment goes toward the principal over time.

How do the extra payment options work?

You can add three types of extra payments. Extra Monthly adds a set amount to every payment starting from a date you pick. Extra Annual adds a lump sum once per year in the month you choose. One-Time adds a single payment in one specific month. All extra money goes toward reducing your principal faster.

Can I use this calculator for a car loan or personal loan?

Yes. This calculator works for any installment loan with a fixed interest rate and equal monthly payments. That includes car loans, personal loans, student loans, and any other loan where you pay the same amount each month over a set term.

What is the amortization schedule?

The amortization schedule is the table at the bottom of the results. It lists every single payment and breaks it into the amount that goes to principal, the amount that goes to interest, and the balance left after each payment. You can view it month by month or year by year.

How does the rate sensitivity table work?

The rate sensitivity table shows what your monthly payment, total interest, and total cost would be at interest rates 2% below and 2% above your entered rate. This helps you see how much a small change in interest rate affects your loan cost. Your current rate is highlighted in the table.

What does the Compare Scenarios feature do?

It lets you put two different loan options side by side. You can change the loan amount, interest rate, term, and payment timing for each scenario. The tool then shows the monthly payment, total interest, total cost, and payoff date for both so you can see which loan is the better deal.

Is the payoff date based on today's date?

Yes. The calculator assumes your first payment starts one month from today. It counts forward from today's date to figure out the month and year your final payment will be made.

What happens if I enter 0% interest?

If the interest rate is 0%, the calculator simply divides the loan amount by the number of months. Your monthly payment equals the principal split evenly across all payments, and you pay no interest at all.

Does this calculator include fees or taxes?

No. This calculator only figures out principal and interest. It does not include origination fees, closing costs, taxes, or insurance. Your actual total cost may be higher if your loan has extra fees.

What is the maximum loan amount and term I can enter?

The loan amount can be up to $9,999,999. The loan term can be up to 360 months, which is 30 years. The interest rate can be between 0% and 25%.

How do I read the principal vs interest bar?

The colored bar near the top of the results shows what share of your total payments goes to principal and what share goes to interest. The blue section is principal, and the orange section is interest. The percentages and dollar amounts are listed below the bar.