What is 1/4 grain (gr) in milligrams (mg)?

• A. 15 mg
• B. 30 mg
• C. 7.5 mg
• D. 60 mg

Answer: (A)

Grains are a traditional unit of mass used for medications. A full grain is about 64.8 mg, so a quarter of a grain is roughly 16.2 mg. In many veterinary contexts, people round grain conversions to simpler numbers, and a common rounding makes a quarter grain about 15 mg. That’s why 15 mg is the best match among the options.

Looking at the other numbers helps confirm this: 30 mg would be about half of a grain under a simple 60 mg-per-grain rule, 7.5 mg is far too low for a quarter grain, and 60 mg would be a full grain.