Interest Calculator
See how much interest your money earns, simple versus compound.
Runs in your browser — nothing is sent or saved.
How to use the interest calculator
- Enter the principal, the starting sum.
- Enter the annual interest rate.
- Enter the number of years.
- Compare the simple and compound interest earned.
How much interest will I earn
This interest calculator answers how much interest a sum earns over time, such as the interest on savings, and it shows two answers side by side. The simple figure charges interest on the principal only. The compound figure, worked out with monthly compounding, charges interest on the principal plus the interest already added. Seeing both makes the cost or benefit of compounding obvious.
Simple vs compound interest
The two methods start the same and then diverge. Simple interest adds the same amount each year, so it grows in a straight line. Compound interest reinvests each period's interest, so the balance curves upward and pulls ahead. The longer the time and the higher the rate, the wider the gap between them, which is why compounding is often called the most powerful force in saving.
When each one applies
Whether your money earns simple or compound interest depends on the product. Most savings accounts, funds, and long-term loans compound. Some short-term loans and bonds use simple interest. If you are comparing offers, check which method each one uses, because the same headline rate can produce different totals.
An estimate, not financial advice
Both figures assume a single steady rate for the whole period. Real rates change, and investments can fall as well as rise. Use this to compare scenarios, not as a promise, and not as financial advice.
FAQ
How much interest will I earn?
Enter your principal, rate, and years. The tool shows the interest earned both as simple interest and as compound interest, so you can see the range and the difference.
What is simple vs compound interest?
Simple interest is charged on the principal only and grows in a straight line. Compound interest is charged on the principal plus past interest, so it grows faster over time.
Why is the compound figure higher?
Because compounding earns interest on interest. Each period's interest is added to the balance and then earns more, so compound interest ends up above simple interest for the same rate.
Which method will my account use?
It depends on the product. Most savings and long-term loans compound; some short-term loans use simple interest. Check the terms of the specific account or loan.
Is my information private?
Yes. Everything is calculated in your browser and nothing you enter is uploaded or saved.