15 mg is equivalent to how many grains?

• A. ¼ Grain (gr)
• B. ½ Grain (gr)
• C. 1 Grain (gr)
• D. 1/8 Grain (gr)

Answer: (A)

Grain is a traditional unit of mass still used on some veterinary medication labels. The conversion is that 1 grain is about 64.8 mg. To convert milligrams to grains, divide the milligrams by 64.8. For 15 mg, 15 ÷ 64.8 ≈ 0.231 grains, which is very close to 0.25 grain (a quarter grain). So 15 mg is best expressed as about a quarter grain.

For context, 1/8 grain is about 8.1 mg, 1/2 grain is about 32.4 mg, and 1 grain is about 64.8 mg, making those options clearly less accurate for 15 mg.