In reality the actual growth rates are likely to be different for each year. If you’re looking to understand CAGR in much greater detail, I recommend reading Investopedia’s article Compound Annual Growth Rate: What You Should Know. CAGR formula. Before we dive into Excel, let’s understand the how calculate the compound annual growth rate. Cumulative growth is a term used to describe a percentage of increase over a set period of time. Cumulative growth can be used to measure growth in the past and, thereby, to plan for population growth, estimate organic cell growth, measure sales growth, and so on.