What are micrograms (mcg)?

The microgram (symbol: mcg or µg) is a unit of mass in the metric system equal to one millionth of a gram (0.000001 g) or one thousandth of a milligram (0.001 mg). It is one of the smallest units of mass commonly used in science, medicine, and nutrition.

Micrograms are frequently used to measure very small quantities, such as vitamins, minerals, medications, and trace elements. For example, vitamin B12 is often measured in micrograms because the human body requires only tiny amounts of it daily.

What are milligrams (mg)?

The milligram (symbol: mg) is a unit of mass in the metric system equal to one thousandth of a gram (0.001 g). It is a commonly used unit for measuring small weights, particularly in medicine, pharmacology, and nutrition.

Milligrams are widely used to express the dosage of medications, the weight of small objects, and the content of nutrients in food. For instance, a standard aspirin tablet typically contains 325 mg of acetylsalicylic acid.

How do you convert micrograms (mcg) to milligrams (mg)?

The Conversion Formula

To convert micrograms to milligrams, divide the number of micrograms by 1000:
Formula: Milligrams = Micrograms ÷ 1000

Alternatively, you can multiply by 0.001:
Milligrams = Micrograms × 0.001

Step-by-Step Process

• Take your value in micrograms
• Divide by 1000 (or multiply by 0.001)
• The result is your value in milligrams

Examples

• 1000 mcg to mg:
  1000 mcg ÷ 1000 = 1 mg
• 5000 mcg to mg:
  5000 mcg ÷ 1000 = 5 mg
• 250 mcg to mg:
  250 mcg ÷ 1000 = 0.25 mg
• 10000 mcg to mg:
  10000 mcg ÷ 1000 = 10 mg
• 500 mcg to mg:
  500 mcg ÷ 1000 = 0.5 mg

Quick Reference

• 1 mcg = 0.001 mg
• 1 mg = 1000 mcg
• 1000 mcg = 1 mg

Why This Conversion Works

The conversion factor 1000 comes from the metric system prefixes. 'Milli-' means one thousandth (1/1000), while 'micro-' means one millionth (1/1,000,000). Since a milligram is 1/1000 of a gram and a microgram is 1/1,000,000 of a gram, there are exactly 1000 micrograms in one milligram.

Tips for Mental Math

Converting micrograms to milligrams is straightforward - simply move the decimal point three places to the left:

1000 mcg → 1.000 mg → 1 mg
500 mcg → 0.500 mg → 0.5 mg
250 mcg → 0.250 mg → 0.25 mg

This method is particularly useful in medical and pharmaceutical contexts where precise dosing is critical.

Micrograms to Milligrams Conversion Table

The conversion of micrograms to milligrams for certain values are provided below: