How to calculate the Average Annual Growth Rate. The Average annual growth rate (AAGR) is the average increase of an investment over a period of time. AAGR measures the average rate of return or growth over constant spaced time periods. To determine the percentage growth for each year, the equation to use is: Percentage Growth Rate = (Ending value / Beginning value) -1. According to this formula, the growth rate for the years can be calculated by dividing the current value by the previous value. BMI Calculator » Triangle Calculators » Length and Distance Conversions » SD SE Mean Median Variance » Blood Type Child Parental Calculator » Unicode, UTF8, Hexidecimal » RGB, Hex, HTML Color Conversion » G-Force RPM Calculator » Chemical Molecular Weight Calculator » Mole, Moles to Grams Calculator » R Plot PCH Symbols » Dilution The geometric mean is also referred as the compounded annual growth rate, as the average rate of return values are calculated based on the product of the terms. It comes from the arithmetic mean but uses multiplication and roots. Investors find the geometric mean value for their investments to get compounding return values.