480 grains per troy ounce.
24 grains per pennyweight.
20 pennyweight per troy ounce.
12 troy ounces per troy pound (which is a “pound” of sterling in the British sense).
Yes, I know- I made a calculator error. The only reason that I tend to use grains is that they are the same whether you’re using troy or avdp., and my scales are in grains.