Compound Interest Calculator

See how your money could grow over time with compound interest and regular contributions.

Free to use • Instant results • Interactive growth chart

Investment Inputs

Live Interactive
$0 – $1,000,000
$
$0 – $20,000
$
0% – 30%
%
1 – 50 years
yrs
Projected Portfolio

Future Value

$343,778
Total Contributions
$130,000
Interest Earned
$213,778
Portfolio Composition
Contributions: 38% ($130,000)
Interest: 62% ($213,778)
Initial Investment
$10,000
Additional Contributions
$120,000
Total Invested
$130,000
Total Growth
$213,778
Interest Earned
$213,778

At the assumed rate over 20 years.

Growth Share
62.2% of final value

Over half of your wealth created by compounding.

Estimated Annual Growth
$10,689 / year

Average annualized earnings over the horizon.

Visual Projection

Investment Growth Over Time

Hover over the chart to inspect your projected balance, contributions, and interest across each year.

Total Balance
Contributions
Interest Earned
Key Checkpoints

Growth Milestones

Estimated portfolio value at major year milestones based on your current inputs.

Sensitivity Analysis

What if your return were different?

Compare potential outcomes with conservative (5%), baseline (8%), and optimistic (10%) market returns using your selected deposits and timeframe.

Scenario Annual Rate Final Value Interest Earned

Illustrative scenarios only. Investment returns are not guaranteed.

Year-by-Year Growth

Detailed annual progression of deposits, compounding interest and accumulated wealth.

Year Starting Balance Contributions Interest Ending Balance
Financial Fundamentals

How Compound Interest Works

Compound interest means you earn returns not only on your original money, but also on previously accumulated returns. Over long time horizons, this snowball effect transforms steady savings into substantial wealth.

1
Initial investment (The Seed)

Your starting lump sum provides the baseline capital that starts generating returns on day one.

2
Regular contributions (The Fuel)

Adding money every month increases the compounding base, smoothing out market entries and supercharging future gains.

3
Returns and reinvestment

Instead of withdrawing dividend payments or earned interest, reinvesting keeps every dollar at work producing more earnings.

4
Long-term compounding exponential curve

In later decades, annual interest generated frequently dwarfs total lifetime out-of-pocket contributions.

The Power of Time

Time can make a big difference

Consider a single $10,000 initial investment growing at an 8% annual return with zero additional contributions. Notice how the growth accelerates as the decades pass:

10 Years
$21,589
+115% Total Gain
20 Years
$46,610
+366% Total Gain
30 Years
$100,627
+906% (10x Initial)

Illustrative example, not a guaranteed return.

Reference Example

Compound Interest Example

Here is an illustrative calculation matching standard assumptions:

Initial Principal
$10,000
Monthly Deposit
$500 / mo
Annual Rate
8.00%
Time Horizon
20 Years
Resulting Balance
$343,778

Over 20 years, total personal cash contributed equals $130,000 ($10,000 initial + $120,000 in monthly additions). Compounding adds $213,778 in pure earnings, resulting in an ending portfolio of $343,778.

Frequently Asked Questions

Compound Interest FAQs

Answers to key concepts regarding compounding mechanics, frequencies, returns, and inflation.

Compound interest is the interest calculated on the initial principal, which also includes all of the accumulated interest from previous periods on a deposit or loan. It can be thought of as "interest on interest", creating exponential expansion over time.
Simple interest is only paid on the original principal sum. If you invest $1,000 at 5% simple interest, you earn $50 every single year forever. With compound interest, your year-two earnings are computed on $1,050, year three on $1,102.50, causing your annual return amount to expand continuously.
More frequent compounding periods (e.g. daily or monthly rather than annually) generate slightly higher effective annual returns because interest begins generating its own returns sooner. While the difference between daily and monthly compounding is modest, the gap between annual and daily compounding is noticeable over decades.
Yes, dramatically. Consistent monthly contributions provide fresh capital for the compounding engine to build upon. Furthermore, automatic monthly deposits help investors practice disciplined dollar-cost averaging regardless of market cycles.
Because compounding operates exponentially rather than linearly, seemingly small rate increases yield enormous differences. For instance, over 30 years, an 8% return produces nearly double the total wealth of a 6% return on the same invested principal.
No. While certificates of deposit (CDs) and high-yield savings accounts offer guaranteed fixed interest rates backed by FDIC insurance, equity and stock market index investments fluctuate and carry risk. Calculator models illustrate hypothetical constant annual rates for long-term planning purposes.
Over 20 or 30 years, steady price inflation reduces the real goods and services a future dollar can buy. By utilizing Finova's inflation adjustment toggle, you can view your future portfolio translated into "today's dollars" to ensure your savings goals provide adequate genuine purchasing power.
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Finova provides estimates for educational purposes only. Actual investment returns, rates, and compounding effects vary over time. This calculator does not constitute financial or investment advice.