$5,000 invested at 10% annual return compounded monthly grows to $13,535 in 10 years — $8,535 of that is compound interest. Adding $200 monthly contributions would grow the total to $54,504.

Key Numbers

• •Starting amount: $5,000
• •Value after 10 years at 10%: $13,535
• •Interest earned: $8,535
• •With $200/month added: $54,504
• •At 10%, money doubles roughly every 7.2 years (rule of 72)