Compound interest calculator
Grow your savings with compound interest.
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- Free
- Private (processed locally)
- No sign-up
The power of compound interest
Compound interest is often described as a saver’s best ally. The principle is simple: your interest itself earns interest. At first the effect is subtle; but over 20 or 30 years, growth becomes exponential.
How to use the calculator
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Enter your initial amount
The sum you invest at the start.
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Add rate, duration and contributions
The annual rate, the number of years and any regular contribution.
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Read the projection
Final amount, total invested and interest earned appear instantly.
Simple vs compound interest
Example: $1,000 invested at 5% per year, no contributions, compounded annually.
| Duration | Simple interest | Compound interest |
|---|---|---|
| 10 years | $1,500 | $1,629 |
| 20 years | $2,000 | $2,653 |
| 30 years | $2,500 | $4,322 |
At 30 years, compound interest yields nearly twice as much as simple interest.
Tips to make the most of it
- Start early: time is the most powerful factor.
- Be consistent: automatic contributions make the difference.
- Reinvest the interest rather than withdrawing it.
This tool provides a projection for information only and is not investment advice. Past returns do not guarantee future returns.
Frequently asked questions
What is compound interest?
It is the mechanism by which the interest earned is added to the principal and, in turn, earns interest. This is “interest on interest”: the more time passes, the faster the growth.
How is it different from simple interest?
Simple interest applies only to the starting principal, whereas compound interest applies to the principal plus the interest already accumulated. Over long periods, the gap becomes substantial (see the table below).
What is the compounding frequency?
It is the number of times per year interest is calculated and added to the principal. Monthly compounding yields slightly more than annual compounding at the same rate.
How do regular contributions change the result?
Each contribution increases the principal and itself earns compound interest. Modest but regular contributions have a dramatic effect over the long term.
Is my data saved?
No. Everything is computed in your browser; no financial information is transmitted.