Calculate simple and compound interest with precision using our free online interest calculator. Understand how your money grows over time with clear explanations, step-by-step results, and visual comparisons.
Total Interest
$0
Final Amount
$0
Enter your values and click "Calculate Interest" to see results
Understanding how interest accumulates helps you make smarter financial choices when saving, investing, or borrowing.
Simple interest is calculated only on the original principal amount throughout the entire time period.
Formula:SI = P × R × T / 100
Compound interest is calculated on both the principal and the accumulated interest, creating exponential growth over time.
Formula:A = P(1 + r/n)ⁿᵗ
Principal: $10,000 | Rate: 5% | Time: 5 years
Interest: $2,500
Total: $12,500
Principal: $10,000 | Rate: 5% | Time: 5 years
Interest: $2,763
Total: $12,763
Difference: Compound interest earns $263 more than simple interest in this example!
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Interest can help your money grow — or increase your debt — depending on whether you’re saving or borrowing.
The initial amount of money invested or borrowed.
The annual cost or return as a percentage.
How often interest is added to your balance.
The total duration of the investment or loan.
See how your deposits grow with compounding.
Estimate returns and compare options.
Understand true borrowing costs.
Project savings for college expenses.
The earlier you start, the greater the impact.
Let interest earn more interest.
Even small rate differences can change outcomes.
Subtract inflation to calculate real growth.
Especially for long-term investments or large loans.
Simple interest is calculated only on the original amount, while compound interest includes both the principal and accumulated interest.
Compound interest is better for savings because it allows your earnings to grow exponentially.
Use the formula A = P(1 + r/n)ⁿᵗ, where P is the principal, r is the annual rate, n is the compounding frequency, and t is time in years.
Yes. Enter your values and select “Monthly” as the compounding frequency to calculate monthly interest.
It’s how often interest is added to your balance — yearly, quarterly, monthly, or daily.
By setting n = 365 in the formula A = P(1 + r/n)ⁿᵗ. This gives you the most frequent compounding growth.
SI = P × R × T / 100 — multiply the principal, annual rate, and time, then divide by 100.
Inflation reduces the real value of your returns. Subtract the inflation rate from your nominal interest rate to get real returns.
APR is the yearly cost of borrowing or investing, including interest and applicable fees.
Yes. It’s completely free, accurate, and available online anytime — no registration required.