Which quantity equals 1 milligram?

• A. 1 centigram
• B. 1 decigram
• C. 1 milligram
• D. 1 gram

Answer: (C)

Understanding metric prefixes helps you compare small masses by using a common base unit, the gram. Milli means one-thousandth, centi means one-hundredth, and deci means one-tenth. So 1 milligram is 0.001 gram, 1 centigram is 0.01 gram, 1 decigram is 0.1 gram, and 1 gram is 1 gram. If you convert to grams (or to milligrams), you get: 0.001 g equals 1 mg; 0.01 g equals 10 mg; 0.1 g equals 100 mg; 1 g equals 1000 mg. The quantity that equals 1 milligram is exactly 1 milligram, since it corresponds to 0.001 gram.