For commercial applications where it is mandated by law to label products accurately, this is a priority situation.
As a home brewer, a half percent abv% is unlikely to be a major concern, but it is nice to be accurate for sure. I use a digital Milwaukee Brix Hydrometer which is tested/calibrated to be quite accurate. From there, you can use calculation programs and determine abv percentages using OG and FG (when alcohol is present).
I am not suggesting the purchase of a digital meter, but I have good results with mine.