Why 325mg can be written as 5 gr?

Answer 1

Since 1959, the official 'grain' (gr) of mass has been defined as 64.79891 milligrams (mg) of mass.

If you have 5 grains (gr) of mass then, you have 323.99455 milligrams (mg) of mass.

Aspirin is manufactured with 5 gr of acetylsalicylic acid in each tablet. Although that's

actually no more than 323.99455 mg of aspirin, the label claims that the pills contain

a full 325 mg each, and you pay for 1.00545 milligram more than you get. Over a full

lifetime, this could add up.