Interest Rate Calculator
Figure out what borrowing could cost you before you agree to a loan.
Whether you’re comparing personal loans or other borrowing options, understanding the estimated interest rate and total repayment can help you make an informed decision. Use the loan interest rate calculator above to estimate your loan costs and better run the numbers before you agree to any offer.
A Simple Guide to the Interest Calculator
The tool is simple to use, but you need to enter the right values to get the right results. This is what each field means:
Loan amount (principal)
This is the total sum you’re borrowing, without including any fees or interest. If you’re calculating for a credit card balance, enter the outstanding amount.
Loan term
This is how long you have to repay the loan. Enter this in months or years, depending on what your lender specifies. A longer term lowers your monthly payment but increases the total interest paid over time.
Monthly payment
This is the amount you are expected to pay each month. If you already know your payment from a loan offer, enter it here.
Try out a few different loan amounts or terms to see how the numbers change. This is helpful before you agree to any loan offer.
How Interest Rates Work
The interest rate is the percentage a lender charges you to borrow the money. It is usually expressed as an annual percentage of the principal, which is the amount borrowed.
APR (Annual Percentage Rate) usually gives a broader view of borrowing costs because it includes the interest rate and certain lender fees. This is why it’s a good idea to compare APRs when you’re looking for a loan. Two loans with the same nominal rate can have very different APRs.
How to Calculate a Simple Interest Rate
To estimate a simple annual interest rate, divide the total interest paid by the amount borrowed, then divide by the number of years. This method provides only an approximation and works best for simple interest loans without compounding.
Where:
- R = simple interest rate
- I = total interest
- P = principal
- t = time in years
If you take out a $1,000 loan and pay $200 in interest over two years, the annual rate is $200 ÷ $1,000 ÷ 2 = 10%. This may be easy to estimate on paper, but it gets a bit more complex when repayment is spread over time or interest is compounded. That’s where a calculator comes in handy.
| Variable | Value | Note |
| Principal | $1,000 | Starting loan amount |
| Total interest paid | $200 | Paid on top of the principal |
| Loan term | 2 years | Repayment period |
| Annual interest rate | 10% per year | $200 ÷ $1,000 ÷ 2 = 0.10 |
Types of Interest Borrowers Encounter
Not all interest works the same way. When you’re looking at offers or estimating costs, it’s important to know the difference.
Simple vs. Compound Interest
Simple interest is calculated only on the principal balance. If you borrow $1,000 at 10% simple interest for three years, you’ll pay $100 a year, for a total of $300. Easy to understand and predictable.
Compound interest is calculated on the principal plus previously accrued interest. Over time, this increases the total borrowing cost. The more often interest compounds (daily, monthly, or yearly), the more you will have to pay.
Credit cards usually use compound interest. This means interest is charged on the outstanding balance, and it can grow over time.
When you have savings accounts and investments, compounding builds your balance over time. With debt, that same effect runs in reverse: your balance grows even when you stop borrowing. One of the first things you should ask any lender is what type of interest applies to your loan.
Fixed vs. Variable Interest Rates
A fixed interest rate stays the same over the loan term, which makes payments more predictable. Many personal loans and mortgages have fixed rates.
A variable interest rate, also called an adjustable rate, can change over time based on a benchmark or index named in the loan agreement. Your payments can change. Variable rates often start out lower than fixed rates, which can be appealing, but they are less certain in the long run. Your payment can rise a lot if market rates climb.
When you borrow money for a short time, the difference between fixed and variable rates doesn’t matter as much because rates don’t have as much time to change. If you want your payments to stay the same, most financial advisors say you should go with fixed rates for loans that last more than one year.
How to Get the Best Interest Rate
The rate you get is based on how lenders see you as a borrower. What really makes a difference is:
- Raise your credit score. Most lenders will give you lower rates if you improve your credit score by even a small amount, like going from 620 to 680. Pay off any debts you already have, get rid of any late payments, and don’t open any new credit accounts right before you apply.
- Lower the ratio of your debt to your income. Lenders want to see how much of your monthly income already goes toward debt payments. The lower this ratio is, the more willing they are to offer better terms.
- Look at more than one lender. For the same loan profile, rates can be very different between banks, credit unions, and online lenders. Getting pre-qualified with a few lenders, which usually only requires a soft credit check, lets you compare without hurting your score.
- Choose a loan with a shorter term. Shorter terms typically have lower rates because the lender’s money is at risk for less time. The tradeoff is that you have to pay more each month.
- Use collateral if appropriate. The lender has a backup plan if you can’t pay back a secured loan. Offering collateral may help you qualify for a lower rate.
Learn more about the difference between secured and unsecured loans.
Frequently Asked Questions
Can this calculator estimate a credit card minimum payment?
You can get close, but each credit card company has its own way of figuring out the minimum payment. Most of the time, they use a formula that sets the minimum as the higher of a percentage of the balance or a flat amount. This calculator works best for fixed-term installment loans. For credit cards, look at your cardholder agreement to find out the exact formula for the minimum payment, or use a special credit card interest calculator.
What's the difference between APR and interest rate?
The interest rate is just the cost of borrowing the money. APR includes that and any other fees, like origination fees, closing costs, and so on, that are spread out over the life of the loan. APR is a better number for comparing loan offers side by side because it gives you a better idea of what you’re really paying.
How do I calculate the interest rate on a loan if I only know my monthly payment?
Enter the loan amount, loan term, and monthly payment into the calculator above. It will calculate the implied annual interest rate. If your lender provided a monthly payment figure without disclosing the rate, ask for clarification before signing the loan agreement.
Does a lower interest rate always mean a cheaper loan?
Not always. A loan with a lower rate but a longer term can cost more in total interest than a loan with a slightly higher rate but a shorter term. Don’t just look at the monthly payment or the rate by itself; always look at the total amount paid back.
What is considered a good personal loan rate?
It depends on your credit history, the lender, and current market conditions. Borrowers with stronger credit usually qualify for lower personal loan rates than borrowers with poor or limited credit. People with bad or limited credit history usually have to pay higher rates. To evaluate a loan offer, use the interest rate calculator to compare the estimated monthly payment, total interest, and total repayment.