How accurate is this device?

I found the device to be relatively accurate for me. For example, I believed that I hit a 7 iron about 150 +/- yards. My reading averaged 149 with a range from about 145 to 155. The distance is a function of ball speed at about a yard from impact, Accordingly, a constant swing speed/ball speed will give a constant distance. Unless you are a professional one doesn’t have a consistent ball speed. If you drop off the obviously great and terrible shots you will get a reasonable distance ball flight average. This device is really only helpful on the range. It can not calculate roll. Higher ball flights will be more accurate than lower ball flights for total distance. It is not a true launch monitor, but for $150 you get a good result without spending thousands.