Starting balance
$10,000
Compound Interest Calculator With Contributions
Estimate how your starting balance, recurring contributions, annual return, and compounding frequency can affect your long-term investment growth.
Press Calculate growth to update the projection with your new assumptions.
Total contributions
$24,000
Interest earned
$25,030
Projected value
$59,030
Portfolio Split
Capital invested vs. interest earnedTotal invested$34,000
Interest earned$25,030
Investment Growth Projection
Solid line: selected scenario. Dotted line: comparison.Year-by-Year Breakdown
Balances shown at the end of each year.| Year | Starting balance | Contributions | Interest earned | Ending balance |
|---|
What Is Compound Interest?
Compound interest is the process of earning returns on both your original investment and the interest that has already been added to your balance. Over long periods, this can create a powerful growth effect because each new return has a larger base to build on.
For investors, compound interest is most useful when money stays invested, returns are reinvested, and contributions continue consistently. The longer the timeline, the more important time and discipline become.
How to Use This Compound Interest Calculator
- Enter your starting balance, such as an existing brokerage account, savings balance, or retirement account value.
- Add an expected annual return. For stocks and ETFs, many people use a long-term average estimate rather than a guaranteed rate.
- Choose how long the money will stay invested and how often returns compound.
- Add recurring contributions and select whether they happen weekly, bi-weekly, monthly, quarterly, or yearly.
- Compare the result with and without contributions to see how much regular investing changes the projection.
Compound Interest Formula
The basic compound interest formula is A = P(1 + r / n)nt. In this formula, A is the future value, P is the starting principal, r is the annual return, n is the number of compounding periods per year, and t is the number of years.
This calculator also includes recurring contributions. Because contributions may happen on a different schedule than compounding, the tool converts the annual contribution amount into the selected compounding period and applies interest period by period.
Example: $10,000 Invested With $200 Monthly Contributions
With a $10,000 starting balance, $200 monthly contribution, 8% annual return, monthly compounding, and 10-year timeline, the projected portfolio value is about $59,030 when contributions are applied before each compounding period. In that scenario, $34,000 comes from your starting balance plus contributions, while about $25,030 comes from compound growth.
Ways to Improve Long-Term Compound Growth
- Start earlier so compounding has more time to work.
- Increase contributions when your income or savings rate improves.
- Keep returns invested instead of withdrawing gains too early.
- Compare recurring investing with lump-sum investing using the right tool for the decision.
- Review assumptions for fees, taxes, inflation, and market volatility before making financial decisions.
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Frequently Asked Questions
What is compound interest?
Compound interest is interest earned on both the original investment and the interest that has already accumulated.
How does this calculator handle contributions?
The calculator converts your contribution schedule into the selected compounding period and adds each contribution before interest is applied for that period.
Does more frequent compounding increase returns?
More frequent compounding can increase the final value when the annual return is the same, although the difference may be small for many long-term investing scenarios.
Can I use this calculator for stocks, ETFs, or crypto?
Yes. It can model any investment where you want to estimate growth using an expected annual return. Actual market returns are uncertain and can be negative.