What is an Interest Rate?
An interest rate is the amount charged by lenders to borrowers for the use of money, expressed as a percentage of the principal, or original amount borrowed. It can also be described as the cost to borrow money. For instance, an 8% interest rate for borrowing $100 a year will obligate a person to pay $108 at year-end.
Interest rates are involved in almost all formal lending and borrowing transactions. Examples include mortgage rates, credit card charges, business loans, retirement fund growth, amortization of long-term assets, and much more. Generally, borrowers want the lowest possible interest rates because it will cost less to borrow, while lenders seek higher rates for larger profits.
How to Use This Interest Rate Calculator
- Enter the Loan Amount: This is the total principal amount of the loan. For example, the price of a car or the mortgage amount on a home.
- Set the Loan Term: Specify the duration of the loan in either years or months. Toggle between the two using the radio buttons.
- Enter the Monthly Payment: Input the fixed monthly payment amount. This is the amount you pay (or would pay) each month.
- Click Calculate: The calculator will determine the annual interest rate, show total payments and interest paid, and generate a full amortization schedule.
Simple vs. Compound Interest
There are two methods for calculating interest. Simple interest is calculated as a percentage of principal only, while compound interest is calculated as a percentage of the principal along with any accrued interest. As a result of this compounding behavior, interest earned by lenders subsequently earns interest over time.
The more frequently interest compounds within a given time period, the more interest will be accrued. Most formal interest payment calculations today are compounded, including those used by this calculator. Any reference to the interest rate in this tool refers to compound interest rather than simple interest.
Fixed vs. Variable Interest Rates
Fixed rates are set as a certain percentage for the life of the loan and will not change. Variable rates can fluctuate over time, generally based on factors such as another interest rate, inflation, or a market index. This Interest Rate Calculator displays results as a fixed interest rate.
Factors That Affect Interest Rates
Several factors influence the interest rates people receive on their loans:
- Credit Score: A higher credit score typically results in more favorable interest rates. Scores above 750 are considered excellent and receive the best rates.
- Loan Term: Longer repayment terms can increase the interest rate because it is riskier for lenders.
- Secured vs. Unsecured: Secured loans (backed by collateral) generally carry lower interest rates than unsecured loans.
- Economic Conditions: Central bank policies, inflation rates, and overall economic activity all influence prevailing interest rates.
- Down Payment: Making a larger down payment can lower the interest rate a borrower is subject to.
Understanding the Amortization Schedule
The amortization schedule shows how each monthly payment is split between principal and interest over the life of the loan. In the early months, a larger portion of each payment goes toward interest. As the loan matures, more of each payment goes toward reducing the principal balance.
This is why making extra payments early in a loan's life can save significant amounts of interest over the long term. Even small additional principal payments can reduce the total interest paid and shorten the loan term.
Frequently Asked Questions
How does the Interest Rate Calculator work?
The calculator uses a numerical method to solve for the interest rate in the standard loan amortization formula. Given your loan amount, loan term, and monthly payment, it finds the annual interest rate that makes the present value of all payments equal to the loan amount.
What is the difference between interest rate and APR?
The interest rate is the cost of borrowing the principal loan amount. APR (Annual Percentage Rate) includes the interest rate plus other fees and costs associated with the loan, such as origination fees and closing costs. APR gives a more complete picture of the total cost of borrowing.
Can I use this for car loans?
Yes. This calculator is ideal for situations where car dealers only provide monthly payment information and total price without including the actual rate on the car loan. Enter the loan amount, term, and monthly payment to discover the real interest rate.
Why is my calculated rate different from my lender's quote?
Your lender may have quoted the APR (which includes fees) rather than the pure interest rate. Additional costs like insurance or origination fees rolled into payments can also cause differences. This calculator determines the mathematical interest rate based solely on the loan amount, term, and payment.
What is an amortization schedule?
An amortization schedule is a table showing each monthly payment broken down into principal and interest portions over the life of the loan. Early payments are mostly interest, while later payments are mostly principal.