Interest Calculator
Calculate simple or compound interest and estimate the final balance from principal, interest rate, time, and compounding frequency.
Simple Interest = P × r × t
Compound Balance = P × (1 + r/n)n×t
1,000 at 5% for 5 years compounded monthly grows to about 1,283.36.
Choose simple or compound interest, enter principal, rate, and time, then calculate.
Use it to estimate savings growth, investment returns, or interest costs.
Common mistakes include using percent instead of decimal rate, wrong compounding frequency, and ignoring fees or taxes.
Examples
Example 1: Simple interest
Principal: 1,000
Rate: 5%
Time: 5 years
Example 2: Compound interest
Principal: 1,000
Rate: 5%
Monthly compounding
Example 3: Daily compounding
More frequent compounding slightly increases the final balance.
Compare frequencies easilyWhen to Use This Calculator
- Savings estimates
- Investment growth
- Interest comparisons
- Education examples
- Loan interest checks
How It Works
- Choose interest type.
- Enter principal, rate, and time.
- Select compounding and calculate.
Common Mistakes
- Confusing simple and compound interest
- Using wrong rate period
- Ignoring fees and taxes
- Expecting guaranteed returns
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Frequently Asked Questions
What is simple interest?
Simple interest is calculated only on the original principal.
What is compound interest?
Compound interest is calculated on the principal and previously earned interest.
Can I change compounding frequency?
Yes. Choose monthly, quarterly, yearly, or daily compounding.
Is this investment advice?
No. It is a calculation tool for estimates only.
Why does compounding matter?
More frequent compounding can increase the final balance over time.