Compound Interest Calculator

Calculates compound interest growth for investments and savings with various contribution patterns, compounding frequencies, and rate scenarios. Visualizes the power of compounding over time.

Usage

Provide the initial investment amount, expected annual return rate, time horizon, and any regular contributions. Specify the compounding frequency (daily, monthly, quarterly, annually) and whether you want inflation-adjusted projections.

Examples

• "Calculate the growth of $10,000 invested at 8% annual return over 30 years with $500 monthly contributions"
• "Compare monthly vs annual compounding on a $50,000 investment at 6% over 20 years"
• "How long will it take to reach $1 million starting with $25,000 and saving $1,000/month at 7% return"

Guidelines

• Always show both nominal and inflation-adjusted (real) returns; 8% nominal at 3% inflation is about 5% real growth
• Compare scenarios side by side: starting early with less vs starting late with more demonstrates compounding's power
• Include the impact of fees; even 1% in annual fees can reduce a 30-year portfolio by 25% or more
• Show year-by-year breakdowns so the accelerating growth curve is visible, especially in later years
• Use conservative return assumptions (5-7% real) for long-term planning rather than optimistic projections