Loan Calculator

How this loan calculator works

Enter your loan amount, interest rate, and term in months to see your monthly payment, total interest, and total amount paid, for any personal loan, auto loan, or other fixed-rate installment loan.

The loan payment formula

M = P × [ r(1+r)^n ] / [ (1+r)^n − 1 ]

M is your monthly payment, P is the loan amount, r is your monthly interest rate (annual rate ÷ 12), and n is the total number of monthly payments. This is the same standard amortization formula used for mortgages, just without property tax or insurance added on.

Step-by-step: how to calculate your payment

Divide your annual interest rate by 12 to get the monthly rate.
Multiply your loan term in years by 12 (or just use months directly if your lender quotes it that way).
Plug the loan amount, monthly rate, and number of payments into the formula above.
Multiply the monthly payment by the number of payments to see the total amount paid, then subtract the loan amount to find total interest.

Worked example

A $20,000 loan at 7.5% APR over 60 months (5 years):

Monthly rate: 7.5% ÷ 12 = 0.00625
Monthly payment: ≈ $401
Total paid over 5 years: ≈ $401 × 60 = ≈ $24,050
Total interest paid: ≈ $24,050 − $20,000 = ≈ $4,050

Common mistakes

Ignoring origination fees. Some personal loans deduct a fee from the amount you actually receive, so your real cost is higher than the advertised rate suggests.
Comparing loans by monthly payment alone. A longer term lowers the payment but increases total interest paid.
Not checking for prepayment penalties if you plan to pay the loan off early.

Tips for a better loan

Compare your rate against your credit union, not just online lenders.
A shorter term almost always means significantly less total interest, if the payment fits your budget.
Making extra payments toward principal, when allowed, shortens the loan and cuts total interest.

What’s a good interest rate for a personal loan?

Rates vary widely based on credit score, typically ranging from around 6% for excellent credit to 20%+ for lower credit scores. Comparing multiple lenders is the best way to find your actual best rate.

Does this calculator work for auto loans?

Yes, the same amortization formula applies to any fixed-rate installment loan, personal, auto, or otherwise.

What’s the difference between a loan calculator and a mortgage calculator?

The math is identical, but our mortgage calculator also factors in property tax and homeowners insurance, which don’t apply to personal or auto loans.

Should I choose a shorter or longer loan term?

A shorter term means a higher monthly payment but less total interest. A longer term lowers your payment but costs more overall, similar to the 15 vs 30-year mortgage trade-off.