Try it: Compound Interest Calculator
Enter a principal, monthly contribution, rate, and time horizon — see the year-by-year chart update with your numbers.
title
Start Calculating Your Growth
Enter your investment parameters on the left to see how compound interest can help your money grow
How Compound Interest Works
Principal Growth
Your initial investment earns interest, which is added to your principal.
Compounding Effect
Interest starts earning interest, creating exponential growth over time.
Regular Contributions
Monthly investments significantly accelerate your wealth building.
Key factors that affect compound growth:
- Interest Rate: Higher rates dramatically increase your final amount over long periods
- Time: The longer you invest, the more powerful compounding becomes
- Contribution Frequency: More frequent compounding (daily vs monthly) yields slightly better returns
- Regular Investments: Consistent monthly contributions can outperform lump-sum investments
The full calculator includes inflation-adjusted purchasing power and the Rule of 72 estimate.
Open the full finance calculatorThe Power of Compounding in Action
Consider two investors:
Sarah (Starts at 25)
Invests $200/month for 10 years, then stops.
Total contributed: $24,000
At 7% return by age 65: ~$295,000
Tom (Starts at 35)
Invests $200/month for 30 years straight.
Total contributed: $72,000
At 7% return by age 65: ~$245,000
Sarah invested 3x less money but ended up with more. That's the power of time and compounding. The earlier you start, the more powerful the effect.
The Compound Interest Formula
A = P(1 + r/n)^(nt)
- A = Future value
- P = Principal (initial investment)
- r = Annual interest rate (decimal)
- n = Compounding frequency per year
- t = Number of years
The more frequently interest compounds (daily vs. monthly vs. annually), the more you earn. Use our Compound Interest Calculator to see the formula in action with your own numbers.
Compound Interest Works Both Ways
While compound interest builds wealth through investments, it also works against you with debt. Credit card interest compounds daily, which is why carrying a balance can quickly spiral out of control. The same exponential growth that works in your favor with savings works against you with high-interest debt.
How to Maximize Compound Growth
- Start as early as possible: Time is the most important factor
- Reinvest dividends and returns: Don't withdraw — let it compound
- Choose higher compounding frequency: Daily or monthly beats annual
- Make regular contributions: Each new contribution starts its own compounding journey
Start Compounding Today
The best investment you can make is starting early. Use our Compound Interest Calculator to see how your money can grow, and our Savings Calculator to set and track your goals.