$1,000 invested at 10% annual return compounded monthly grows to $2,707 in 10 years — $1,707 of that is compound interest. Adding $200 monthly contributions would grow the total to $43,676.

Key Numbers

• •Starting amount: $1,000
• •Value after 10 years at 10%: $2,707
• •Interest earned: $1,707
• •With $200/month added: $43,676
• •At 10%, money doubles roughly every 7.2 years (rule of 72)