$5,000 invested at 7% annual return compounded monthly grows to $40,582 in 30 years — $35,582 of that is compound interest. Adding $200 monthly contributions would grow the total to $284,577.

Key Numbers

• •Starting amount: $5,000
• •Value after 30 years at 7%: $40,582
• •Interest earned: $35,582
• •With $200/month added: $284,577
• •At 7%, money doubles roughly every 10.3 years (rule of 72)