Of course! I haven't heard of weighing yourself, but I bet it could work!
Do you happen to have a kitchen scale? If so, you might get a more accurate weight. I have a digital kitchen scale, and I like to wrap it in plastic wrap (for sanitary reasons) before putting a chicken on.
Depending on the scale, you can not only get their weight in pounds, but you can get additional information, such as their additional weight in ounces. For example, it may say that your chicken weighs 5 pounds and 3 ounces, which can help you determine the correct dosage even more accurately.
I hope this helped!