What Is an Installment Loan Calculator?
An installment loan is any loan repaid in equal, scheduled payments over a fixed term — personal loans, auto loans, and many home and student loans all work this way. This calculator finds the fixed monthly payment that fully pays off your loan, along with the total interest and total amount you will pay by the end of the term.
How to Use It
Enter three values: the loan amount (principal), the annual interest rate as a percentage, and the term in months. The calculator instantly shows your level monthly payment plus a breakdown of principal, total interest, and total cost.
The Formula Explained
The payment uses the standard amortization formula: $$M = P \cdot \frac{r\,(1+r)^{n}}{(1+r)^{n}-1}$$ where \(P\) is the principal, \(r\) is the monthly rate (annual rate divided by 12 and by 100), and \(n\) is the number of monthly payments. Multiplying the payment by \(n\) gives the total paid; subtracting the principal isolates the total interest. When the rate is 0%, the payment simply equals the principal divided by the number of months.
Worked Example
Borrow $10,000 at 6% annual interest over 36 months. The monthly rate is \(0.06 \div 12 = 0.005\). Using the formula, the payment is about $304.22. Over 36 months you pay roughly $10,951.91, of which about $951.91 is interest.
FAQ
Does this include fees or insurance? No — it calculates principal and interest only. Origination fees, taxes, or insurance would add to your real cost.
What rate should I enter? Use the nominal annual percentage rate (APR is close for simple installment loans). The calculator converts it to a monthly rate automatically.
Can I use it for a 0% loan? Yes — enter 0 for the rate and the payment becomes the loan amount evenly split across the term.
