What is the compound interest formula?

The classic compound interest formula is A = P(1 + r/n)^(nt), where A is the future balance, P is the principal amount, r is the annual interest rate (in decimal), n is the compounding frequency per year, and t is the investment horizon in years. With regular periodic contributions, annuity summation formulas are combined with the principal compounding.

How does compounding frequency impact returns?

More frequent compounding (such as daily or monthly vs annually) generates slightly higher returns because interest earned earlier starts earning interest sooner. For example, $10,000 at 8% compounded annually yields $21,589 in 10 years, whereas daily compounding yields $22,253.

What is the Rule of 72 in investing?

The Rule of 72 is a quick mental formula to estimate how many years it takes for your investment to double. Simply divide 72 by your annual expected return percentage. At an 8% annual return, your money doubles in approximately 72 / 8 = 9 years.

What is the 'Tipping Point' in compound interest?

The Tipping Point is the financial milestone where the compound interest earned in a single year exceeds the total amount of new money you contribute that year. Beyond this point, your wealth growth is driven primarily by compound momentum rather than your active savings.

Compound Interest Calculator | Investment Growth, Monthly Contributions & Inflation

Investment Parameters

Initial Starting Principal

Regular Contribution

Deposit Frequency

Annual Interest Rate / Return (%)

4.5% (HYSA) 7.0% (Conservative) 8.5% (S&P 500 Avg) 10.0% (Stock Growth) 12.0% (Aggressive)

Investment Horizon (Years): 20 yrs

Compounding Frequency

Advanced Levers (Inflation & Step-Up)

Annual Inflation Rate (%/yr)

Annual Contribution Step-Up (%)

Deposit Timing

Estimated Tax on Gains (%)

3-Way Rate Comparison

Conservative (6%)

Your Rate (8.5%)

Aggressive (12%)

 Total Future Value
$0
0x your total investment

Total Principal Invested

Initial + Regular deposits

Compound Interest Earned

0% of total wealth

Inflation-Adjusted Value

Today's purchasing power

Rule of 72 Doubling

Every 8.5 Years

The "Tipping Point"

Year 7

Portfolio Growth Over Time

Principal

Total Balance

Real (Inflation)

Year-by-Year Schedule

Year	Contributions	Interest (Year)	Total Interest	Ending Balance

Mastering Compound Interest & Wealth Building

How does Compound Interest work?

Compound interest is interest calculated on both the initial principal and the accumulated interest from prior periods. Often dubbed the "eighth wonder of the world," compound growth starts gradually and accelerates exponentially over long investment horizons.

The Impact of Regular Dollar-Cost Averaging

Consistently contributing a set amount every month (dollar-cost averaging) significantly amplifies the compounding curve. As you purchase more shares during market dips and fewer during peaks, your compounding base snowballs rapidly.

Why Inflation Adjustment Matters

A $1,000,000 portfolio 30 years in the future will not have the same purchasing power as $1,000,000 today. Our calculator discounts future returns using your estimated inflation rate (historically ~2.5% - 3.5%) to show your true purchasing power in today's money.

What is Continuous Compounding?

Continuous compounding represents the mathematical upper bound of compounding frequency, modeled by the formula A = P * e^(rt). It calculates growth assuming interest is generated and reinvested at every infinitesimally small instant of time.