Be sure the cell range in the IRR formula always starts with the lump-sum cell in Column C and ends with the age you want. For example, =IRR (C1:C18) would be the formula used at age 80 in Column D.

Do you feel lost trying to decide what to invest in? What if you had a tool to help you identify the best potential path forward? That’s how you can look at the internal rate of return (IRR): as a ...