I joined a gym last summer and the echocardiogram was mandatory when you joined. Anyway it gave me a full report about my lean muscle mass and fat composition. It said I was 137.38lbs muscle mass(shocking to me!) and I was 251.5lbs at the time, so I had 45.2% BF.

I am going by the body fat calculator at self.com because when I fed in my info from when I had my test done, it gave my about the same result as my echocardiogram.

I think any of them are fine, as long as you use the same one, it'll accuratly show you how your BF is dropping.