Compound Interest Calculator

How to read your results

This calculator is designed to give you a fast, directional answer — not to replace personalized financial advice. Use the results as a starting point for a conversation with a fee-only Certified Financial Planner. Small changes to inputs (a 0.5% higher rate of return, a $50 higher monthly contribution) compound into meaningfully different long-term outcomes, so try adjusting one variable at a time.

Assumptions we make

• Rates of return are averaged and do not reflect year-to-year volatility.
• Inflation is not automatically applied unless noted.
• Taxes on investment gains are excluded — use tax-advantaged accounts (401(k), Roth IRA, HSA) where possible.