Well if you live in uk a 20bag is normally an eigth although a 20bag doesnt nessceraily (sp) mean an eigth just means an amount of weed that costs £20 and a 20bag is normally between 2.8g - 4.0 (if u gotta rly good dealer that does nice bags) so anything between 5.6g - 8.0 but should by around 7 grams anyway