Pay Off Debt vs Invest Calculator

About this calculator

This calculator compares two paths for extra cash: paying down debt at its interest rate (a guaranteed, risk-free return equal to that rate, since every dollar of principal paid off is a dollar of interest never charged) versus investing the same amount and letting it compound at an expected market return over the same number of years, using standard compound growth: FV = P × (1 + r)ⁿ for each path.

The math is simple, but the decision financial advisors and personal finance educators walk clients through has real nuance: a 22% credit card APR is essentially never beaten by expected stock market returns, so paying it off first is close to a mathematical certainty, while a 4% mortgage or student loan sits close enough to typical long-run equity returns (historically ~7–10% nominal for the S&P 500) that risk tolerance, tax treatment (mortgage interest deduction, retirement account matching), and the psychological value of being debt-free start to matter as much as the raw numbers.