PercentLab

Loan Interest Calculator

Calculate total loan interest, monthly payments, and payoff schedule. Perfect for personal loans, auto loans, and student loans.

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Formula

Monthly Payment = P[r(1+r)^n]/[(1+r)^n-1] where P=principal, r=monthly rate, n=number of payments

Example

loan Amount:20000
interest Rate:6
loan Term:5
monthly Payment:386.66
total Interest:3199.6
total Paid:23199.6

Frequently Asked Questions

For monthly payments, use the amortization formula: M = P[r(1+r)^n]/[(1+r)^n-1]. Total interest = (Monthly Payment × Number of Months) - Loan Amount. For a $20,000 loan at 6% for 5 years: monthly payment = $386.66, total interest = $3,199.60.

Interest rate is the cost of borrowing the principal. APR (Annual Percentage Rate) includes the interest rate plus other fees and costs. APR is always equal to or higher than the interest rate.

Make extra payments toward principal, refinance to a lower rate, choose a shorter loan term, or make bi-weekly instead of monthly payments. Even small extra payments can save thousands in interest.

Amortization is the process of paying off a loan through regular payments. Early payments are mostly interest, later payments are mostly principal. An amortization schedule shows the breakdown for each payment.

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Last updated: 2025-11-13