What happens to $5,000 at 8% over 15 years?
If you invest $5,000 today at a 8% annual interest rate and leave it untouched for 15 years — with interest compounding annually — you end up with $15,860.85. That means your original principal earns $10,860.85 in compound interest, bringing your total return to 217.2% over the investment period.
The key driver is compounding: each year you earn interest not only on your original $5,000, but also on all the interest that has accumulated in prior years. In year one you earn $400.00, but by year 15 that annual interest payment grows to $1,174.88 — the same percentage applied to a much larger base.
At 8%, money doubles approximately every 9.0 years (Rule of 72: 72 ÷ 8 = 9.0). Over a 15-year horizon that translates to a 3.17x growth multiple.
These figures assume a constant 8% rate, annual compounding, and no withdrawals or additional deposits. Use the interactive calculator below to model monthly contributions, different compounding frequencies, or any custom scenario.