Compound Interest Calculator
Project the growth of your trading capital with compound interest, regular contributions, and drawdown simulation.
Your starting investment
Amount you add each month (optional)
Final Balance
$0Total Contributions
$60,000Total Return
$42,231Return %
60.3%Why Compound Interest Matters
Albert Einstein reportedly called compound interest the 'eighth wonder of the world'. In investing, it's the engine that turns consistent savings into life-changing wealth over time.
The key insight: you don't need to pick winners. A steady 8% annual return with monthly compounding doubles your money every ~9 years. Starting with $10,000 at 8% with $500/month contributions, you'd have over $700k after 30 years.
Time is your biggest advantage. The first decade feels slow because growth is linear. But as the base grows, the curve steepens. This is why starting early matters more than the amount you start with.
Real Examples
$10,000 · 8% annual return · 30 years
Common Mistakes
#1: Underestimating Time
What traders do
Starting later and expecting the same result, or quitting after a year because 'compounding isn't working'
The consequence
Starting 10 years later with the same contribution requires 3× the monthly deposit to catch up. The first decade is the hardest because growth looks linear — most of the wealth appears in the final years.
What to do instead
Start as early as possible. Even small amounts compound into significant sums given enough time.
#2: Ignoring Fees and Taxes
What traders do
Using gross return assumptions without deducting management fees, expense ratios, and taxes
The consequence
An 8% gross return at 1% fees + 15% tax on gains reduces effective return to ~5.9%. Over 30 years, that's the difference between $700k and $450k on a $10k+$500/month portfolio.
What to do instead
Always use net-of-fee return estimates. Small fee differences compound into huge gaps over decades.
#3: Chasing High Returns
What traders do
Chasing 20%+ returns through risky investments, ignoring that a 40% drawdown erases years of compounding
The consequence
A 40% drawdown on a $100k portfolio requires 67% gain to recover. At 8% annual return, that's over 6 years of growth wiped out. The high return rarely compensates for the volatility.
What to do instead
Focus on consistent returns with controlled drawdowns. Compounding rewards longevity, not heroics.
The Math Behind Compound Interest
Step 1: Calculate the monthly rate
r = (1 + annualRate)1/12 - 1
Example: (1 + 0.08)1/12 - 1 ≈ 0.64% monthlyStep 2: Apply the FV formula
FV = PV × (1 + r)t + PMT × ((1 + r)t - 1) / r
where t = total months, PMT = monthly contributionStep 3: Adjust for drawdowns
After Drawdown: balance × (1 - drawdown%)
Then compounding resumes from the reduced balanceStep 3: Adjust for drawdowns