The following utility will enable you to convert mass/weight expressed in grammes to hundredweight
To convert grammes to hundredweight divide by 50802.35
You've got 0.3 grammes of gold but someone only wants to buy that in units of hundredweight, to change the units divide by 50802.35. Now you have 0.00000591 hundredweight.
To convert 4 grammes into hundredweight divide by 50802.35 giving 0.00007874 hundredweight.
You have 9.5 grammes of silver but you need to know how many hundredweight that is. To get the answer divide by 50802.35 which gives you 0.000187 hundredweight.
How many hundredweight of platinum are there in 5.1 grammes? Just divide by 50802.35 to get the answer of 0.00010039 hundredweight.
In 8.3 grammes of ruby's there are 0.00016338 hundredweight, to achieve this take 8.3 and just divide by 50802.35.