Calculator inputs
Enter the principal amount, annual interest rate, and time period in years.
Enter the amount in the currency you are using. Keep the same currency across money fields.
Enter the annual percentage rate, not a decimal. For example, enter 6.5 for 6.5%.
Enter the length of the period using the unit shown in the label.
Formula
rate = annual rate ÷ 100
final balance = principal + interest
Example: $10,000 at 5% simple interest for 5 years earns $2,500 in interest, for a final balance of $12,500.
Worked examples
$5,000 at 4% for 3 years = $600 interest, $5,600 total
$10,000 at 5% for 5 years = $2,500 interest, $12,500 total
$20,000 at 6% for 10 years = $12,000 interest, $32,000 total
Using this calculator effectively
This page keeps the calculator, formula, examples, and related tools together so you can check the result, understand the method, and move to the next useful calculator when needed.
Accuracy and use of results
CalculatorWorks aims to make calculations clear and practical. We use standard calculation methods where possible, explain assumptions in plain language, and encourage users to verify important results before relying on them.
Simple interest calculator FAQ
What is the difference between simple and compound interest?
Simple interest is calculated only on the original principal. Compound interest is calculated on the principal plus previously earned interest.
Is simple interest common for long-term investments?
Long-term investment growth is usually better represented by compound interest because returns are commonly reinvested or accumulate over time.
Can I use months instead of years?
Convert months to years first. For example, 6 months is 0.5 years and 18 months is 1.5 years.
Does this calculate loan repayments?
No. It estimates interest only. Use a loan repayment calculator if you need scheduled payments, amortization, or monthly payment estimates.
Compare simple interest with other calculators
Simple interest is only one interest model. If interest compounds, or if payments are made over time, use a more specific calculator before making decisions.
When to use simple interest
- Estimating interest on a loan or note that does not compound.
- Checking a classroom finance example.
- Comparing simple interest against compound interest growth.
- Understanding the basic relationship between principal, rate, and time.
Simple interest examples
Example 1: $5,000 at 6% for 3 years earns $900 in simple interest, giving a total of $5,900.
Example 2: $12,000 at 4.5% for 2 years earns $1,080 in simple interest, giving a total of $13,080.
Simple interest formula
Use the annual rate as a percentage and time in years. The final balance is the original principal plus the simple interest amount.
What simple interest means
Simple interest is interest calculated only on the original principal. Unlike compound interest, it does not add earned interest back into the balance for future interest calculations.
This makes simple interest useful for quick estimates, short-term lending examples, education, and comparisons where interest does not compound.