Interest Calculator

Calculate compound interest and investment growth over time

Last updated: 2026-05-13

Simple vs Compound Interest Comparison

Compare the return differences between simple and compound interest under the same conditions

Principal (USD)

Annual Interest Rate (%)

Investment Period (Years)

Compound Frequency

Compound Interest Growth

Interest formulas

This calculator compares simple interest with compound interest so you can see how reinvested interest changes growth over time.

Simple interest = P x r x t
Simple total = P x (1 + r x t)
Compound total = P x (1 + r / n)^(n x t)
Compound interest = Compound total - P

P: Principal; Initial deposit, investment, or balance.
r: Annual rate; Annual interest rate expressed as a decimal.
t: Time; Number of years.
n: Compounding frequency; Number of compounding periods per year.

How this interest calculator works

The calculator applies deterministic interest formulas. It does not predict market returns or account for fees, taxes, inflation, or changing rates.

Convert the annual percentage rate into a decimal value.
Calculate simple interest as principal times rate times time.
Calculate compound interest by applying the selected compounding frequency over the full time period.
Show the difference between simple and compound growth for comparison.

Important notes

Actual account yields may use APY, daily balance methods, minimum balance rules, fees, and tax treatment.
Investment returns are not guaranteed and may be negative.
For borrowing, compounding and fees can increase total repayment cost beyond the simple examples shown here.

Sources

Financial disclaimer

This interest calculator is for informational planning only. It is not investment advice, lending advice, tax advice, legal advice, or a guarantee of future returns.

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