Interest Calculator
Calculate simple or compound interest earned on a lump-sum deposit or investment.
Reviewed October 7, 2026 Runs in your browser — inputs are never stored
Interest earned
$6,470.09
- Final balance
- $16,470.09
- Simple interest$15,000.00
- Compounded yearly$16,288.95
- Compounded monthly$16,470.09
- Compounded daily$16,486.65
Starting principal
This tool provides general financial estimates for educational purposes only and is not personalized financial, tax, or investment advice. Consult a licensed financial professional before making major financial decisions.
About the Interest Calculator
The interest calculator compares simple and compound interest on the same deposit so you can see exactly how much compounding adds. Simple interest is paid only on the original principal, while compound interest is paid on the principal plus the interest already earned. The difference is small over a year or two and large over a decade. Enter a principal, an annual rate, the number of years and how often interest compounds — annually, semi-annually, quarterly, monthly or daily — and the tool returns the final balance and total interest under both methods. It is useful for understanding savings accounts, certificates of deposit and bonds, and for checking the numbers a bank quotes you.
How to use it
- 1Enter the starting principal.
- 2Enter the annual interest rate as a percentage.
- 3Enter how many years the money will stay invested.
- 4Choose the compounding frequency from the list.
- 5Press Calculate to compare simple and compound interest side by side.
Worked example
$10,000 at 5% for 10 years earns $5,000 of simple interest, for a final balance of $15,000. With monthly compounding the balance grows to about $16,470, so compounding adds roughly $1,470. Compounded annually instead, the balance is about $16,289.
How it works
Formulas
Simple: I = P × r × t
Compound: A = P × (1 + r/n)^(n·t)
Difference
Simple interest is earned only on the principal. Compound interest is earned on the principal plus previously accumulated interest.
Who it is for
Savers comparing accounts, students learning the difference between simple and compound interest, and anyone checking a bank’s quoted return.
Why it helps
Seeing both methods side by side makes the value of compounding, and of compounding frequency, concrete.
Common use cases
- Comparing a savings account that compounds monthly with one that compounds annually
- Estimating interest on a certificate of deposit
- Checking homework on simple versus compound interest
- Estimating interest owed on a simple-interest personal loan
Frequently asked questions
A:Compound interest, because you earn interest on your interest over time.
A:More frequent compounding (e.g. daily vs annually) slightly increases the final balance.
A:Results are gross figures and do not account for taxes or inflation.
Reviewed for accuracy · Last updated October 7, 2026
Formulas follow standard amortization, present/future value, and compounding mathematics used throughout the financial industry, and are periodically checked against reference calculations.
CalcWisee Editorial Team
Calculator development and formula review
CalcWisee is an independent site founded by Ayman. Every calculator is built from a published formula or official definition, tested against hand-worked examples before it goes live, and corrected promptly when a reader reports an issue to ayman@calcwisee.com.
Expertise: Financial mathematics, Health and fitness formulas, Applied mathematics, Unit conversion standards
References & sources
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