$1,000 invested at 7% annual return compounded monthly grows to $8,116 in 30 years — $7,116 of that is compound interest. Adding $200 monthly contributions would grow the total to $252,111.

Key Numbers

• •Starting amount: $1,000
• •Value after 30 years at 7%: $8,116
• •Interest earned: $7,116
• •With $200/month added: $252,111
• •At 7%, money doubles roughly every 10.3 years (rule of 72)