Interest Rate Calculator – Calculate the Rate Online
Find the interest rate implied by a loan amount, payment and term.
About the Interest Rate Calculator
What is the Interest Rate Calculator?
An interest rate calculator works backwards: given a loan amount, the payment, and the term, it solves for the interest rate.
Why use this calculator?
Lenders sometimes quote a payment without clearly stating the rate. Solving for the rate reveals what you are really being charged so you can compare offers fairly.
How to use it
- Enter the amount financed.
- Enter the quoted monthly payment.
- Enter the term in months.
- Read the implied annual interest rate.
Formula
Solved numerically by bisection on M = P·r(1+r)^n / ((1+r)^n − 1).
This is the nominal annual rate; the APR may be higher if fees are included.
Frequently Asked Questions
Why is the calculated rate different from the quoted rate?
Fees, insurance or a different payment definition can cause a gap. The number here is the pure interest rate implied by the payment and term.
Can the rate be negative?
Not on a normal loan. If total payments equal the principal the rate is zero; the calculator requires payments above principal to find a positive rate.
What is the difference between principal and interest?
The principal is the amount you borrow. Interest is the fee charged for borrowing it, shown either as an annual rate (APR) or a periodic rate. Early payments go mostly toward interest; later payments go mostly toward principal.
How does the loan term affect my payment?
A longer term lowers the monthly payment but increases the total interest you pay over the life of the loan. A shorter term raises the monthly payment but costs less overall.
What is an amortization schedule?
It is a table that breaks every payment into its principal and interest portions and shows the remaining balance after each payment.
Should I make extra payments?
Extra payments reduce principal directly, which shortens the loan and cuts total interest. Many loans have no prepayment penalty, but check your agreement first.
What is APR and how is it different from the interest rate?
The interest rate applies only to the balance. The APR (annual percentage rate) also includes fees and points, so it reflects the true yearly cost of the loan.
What is compound interest?
Compound interest is interest earned on both your original money and on previously earned interest. Over time it can make savings grow much faster than simple interest.
What is the difference between nominal and effective return?
The nominal return ignores compounding within the year, while the effective (annualised) return accounts for it. The effective figure is usually higher and better reflects real growth.
How does inflation affect my returns?
Inflation erodes purchasing power. The real return is the nominal return minus inflation, so an investment can grow in dollars yet still lose value in what it can buy.