$5,000 invested at 10% annual return compounded monthly grows to $99,187 in 30 years — $94,187 of that is compound interest. Adding $200 monthly contributions would grow the total to $551,285.

Key Numbers

• •Starting amount: $5,000
• •Value after 30 years at 10%: $99,187
• •Interest earned: $94,187
• •With $200/month added: $551,285
• •At 10%, money doubles roughly every 7.2 years (rule of 72)