I was just outside and weighed my full, un-touched nitrous bottle, it's a 5lb bottle and full it weighs 8lbs exactly so that must mean that when full, a 5lb bottle holds approximatley 3lb's of Nitrous oxide. so going by that, half full will be approx. 6.5lbs and when its empty its going to weigh near on 5lbs again.



Hopefully this is some use to someone.

 

If it's a 5 Lbs. bottle, that means it holds 5 Lbs. of nitrous. That's how the guy filling it knows it's full. You put it on a scale empty and fill it until the weight increases by 5 Lbs. Your bottle should weigh about 3 Lbs. empty.

 

Ya what he said