Interest Calculators | Simple & Compounded Interest Calculators
Interest Calculators
Interest Calculators
Use these free interest calculators to estimate how interest grows on savings, investments, loans, and debt. Understanding how interest works can help you compare borrowing costs, evaluate investment growth, and make smarter financial decisions.
This page includes calculators for:
- Simple Interest
- Compound Interest for savings and investments
- Compound Interest for loans and debt
These tools allow you to estimate how interest accumulates over time based on your principal amount, interest rate, and time period.
Our Interest Calculators
Simple Interest Calculator
The Simple Interest Calculator estimates interest based on the standard simple interest formula:
Simple Interest Formula
Interest = P × R × T
Where:
- P = Principal (starting amount of money)
- R = Interest rate (APR)
- T = Time in years
Simple interest is calculated only on the original principal balance. The interest amount does not increase based on previously earned interest.
Many auto loans, personal loans, and mortgages are structured using simple interest. In these loans, interest is typically calculated at regular intervals—such as daily or monthly—based on the remaining loan balance.
This calculator helps you estimate:
- Interest growth based on loan term
- Total interest paid over time
- Total loan cost
Compounded Interest Calculator
The Compounded Interest Calculator estimates how interest grows when interest earnings are added back to the principal balance and continue earning interest.
With compound interest, interest is calculated on both:
- the original principal, and
- the accumulated interest from previous periods.
Interest may compound at different intervals, including:
- Daily
- Monthly
- Quarterly
- Annually
The more frequently interest compounds, the faster the balance grows.
Compounded interest is commonly used in:
- savings accounts
- investment accounts
- retirement accounts
- credit cards and certain types of loans
Investment accounts often follow a similar principle by reinvesting dividends and earnings, allowing the investment to grow faster over time.
Use our compounded interest calculators to estimate:
- long-term financial projections
- investment growth
- savings accumulation
- compounded interest on debt
FAQ
Understanding the difference between simple interest and compound interest is important when evaluating loans and investments.
Here is a real-world example comparing the two:
Loan Example
- Loan Amount: $100,000
- Interest Rate: 10% APR
- Loan Term: 10 years
Simple Interest Total
Total Interest Paid: $100,000
Compound Interest (Daily Compounding)
Total Interest Paid: $171,790.96
Compound interest results in $71,790.96 more interest over the same period.
This example shows how compounding interest can significantly increase the total cost of a loan—or significantly increase investment growth when saving money.
Why Understanding Interest Matters
Interest plays a major role in borrowing, saving, and investing. Knowing how interest works can help you:
- compare loan offers
- estimate borrowing costs
- evaluate investment returns
- plan long-term savings goals
Use the calculators on this page to experiment with different interest rates, compounding periods, and time frames to better understand how interest affects your finances.
APR (Annual Percentage Rate) is the simple interest rate, while APY (Annual Percentage Yield) reflects the total interest earned including the effect of compounding over a year.