It's even messier than laid out above. Attempts at conversion are futile. While the units used may be coverted easily enough, the real problem is that use of different units implies different methods of measurement. So we have the traditional British method which measures backthrust with a crusher, we have the US SAAMI system which measures chamber pressure with either a crusher or pizo transducer, and we have the European CIP system which measures not chamber pressure but throat pressure with either a crusher or transducer. Five different methods that will yield five different results on one single load. Now throw in the usual measurement errors.