ToolkitBook
Determine exactly how your money grows over time. This tool allows you to compare simple and compound interest side-by-side to identify the most profitable strategy. Enter your principal amount, adjust interest rates by day, month, or year, and view instant results. Simple interest calculates returns based solely on your original deposit, while compound interest reinvests your earnings to accelerate growth.
| Bank Type | 1 Year | 2 Years | 3 Years | 5 Years |
|---|---|---|---|---|
| Major Banks (US) | 4.50% | 4.25% | 4.00% | 3.75% |
| Online Banks | 5.00% | 4.75% | 4.50% | 4.25% |
| Credit Unions | 4.75% | 4.50% | 4.25% | 4.00% |
* Rates are for reference only. Actual rates may vary by institution and market conditions.
This calculator provides a clear breakdown of financial growth through two primary interest models.
Simple interest calculates earnings based strictly on the original principal. The formula is: Interest = Principal × Rate × Time. For example, if you deposit $10,000 at a 5% annual interest rate for 3 years, you will earn $1,500 in total interest. In this scenario, your money generates exactly $500 each year, regardless of how much interest has already accumulated. Simple interest is most commonly used for short-term personal loans, certain auto loans, and specific types of bonds. For borrowers, this model is generally preferable because it results in lower total costs compared to compounding.
Compound interest adds your earned interest back into the principal balance, creating a "snowball effect" of exponential growth. The formula is: Total = Principal × (1 + Rate/n)^(n×Time), where n represents the number of times interest is compounded per year. A $10,000 deposit at 5% compounded annually for 3 years yields a total of $11,576.25—which is $76.25 more than the simple interest version. The frequency of compounding is a major factor: returns increase as you move from annual to monthly or daily compounding, as your interest begins earning its own interest much sooner.
The calculator provides a three-part breakdown: the original principal, the total interest earned (or charged), and the final total value. "Interest Earned" represents your net profit on an investment or the total cost of a loan. "Total Value" is the final balance at the end of the term. These figures are essential for comparing different financial products; for instance, a mere 0.5% difference in interest on a $50,000 deposit can result in hundreds of dollars in additional earnings over 10 years.
You can use this tool to compare high-yield savings accounts and see how different APYs (Annual Percentage Yields) impact your long-term wealth. It is also useful for evaluating CD terms—such as comparing a 1-year CD at 4.5% against a 5-year CD at 4.0%. For those planning for the future, you can model retirement growth by entering your current savings and an expected rate of return. A $100,000 portfolio with a 7% annual return would grow to over $760,000 in 30 years through the power of compounding.