Compound Interest

Watch Your Money
Grow Over Time

The most powerful force in finance, visualised.

Your Numbers
Initial Investment
The amount of money you start with before making any contributions.
Annual Interest Rate
The yearly return rate. S&P 500 has averaged around 10% a year before inflation. This site plans with 7% a year, a cautious long-run figure after inflation.
Time Period
Compounding Frequency
How often interest is calculated and added to your balance. More frequent = more growth.
Monthly Contribution
Adjust for Inflation Shows real purchasing power
Inflation Rate
Add pension tax relief UK basic rate: every £80 you pay in becomes £100
Total Value
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Total Invested
—
Interest Earned
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Enter your numbers to see how your wealth compounds over time.
Growth Over Time
Balance trajectory · year by year
Year-by-Year Breakdown
Year Balance Invested Interest Return
🎯 Goal Planner

How Much Should
I Save Monthly?

Set your wealth target. We'll tell you the exact monthly savings needed.

Goal Settings
Target Wealth
$
Starting Amount
$
Annual Interest Rate
%
Time to Goal
Compounding
Monthly Savings Needed
—
to reach your goal
Your Goal
—
You'll Invest
—
Interest Earns
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Your Path to the Goal
⏱ Time Is Money

Start Now vs.
Start Later

Every year you delay costs more than you think. See the real price of waiting.

Scenario Settings
Monthly Investment
$
Annual Return Rate
%
Total Years
Years You Delay
Start Now

If you begin today

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—

If you wait 5 years

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—
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The cost of waiting: money you can never get back
Growth Comparison
The book behind the calculator

Planting Money Trees

The simple way to build wealth, for everyone who was never shown how.

From a working-class upbringing in Darwen to a plan anyone can follow: how compound interest really works, where to find the money, which accounts to open and how to keep going when markets fall. Written for the UK, in plain English.