The SunCalc provides gardeners with the ability to maximize plants growing potential by placing them in optimum light conditions. It measures the amount of accumulated light that falls on a specific location. This provides gardeners with the ability to match a plant's nursery tag light requirements (full sun, partial sun, etc.) with the actual light conditions as measured by SunCalc. All gardeners need to do is place SunCalc at the desired location, turn it on and 12 hours later return to read the results. Full Sun, Partial Sun, Partial Shade or Full Shade.