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Micrograms to Milligrams (mcg to mg) Converter

Convert between micrograms and milligrams using SI prefix definitions. Both directions supported with adjustable decimal precision.

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How SI Prefixes Work

Micro (µ or mcg) is the SI prefix for 10⁻⁶ and milli is the SI prefix for 10⁻³. This means there are 1,000 micrograms in 1 milligram. To convert between these units, you divide when going from smaller to larger units (mcg → mg) and multiply when going from larger to smaller units (mg → mcg).

Formulas

mcg → mg: mg = mcg ÷ 1,000
mg → mcg: mcg = mg × 1,000

Worked Examples

Example 1: Convert 250 mcg to mg

1

mg = 250 ÷ 1,000

2

mg = 0.25

Answer: 0.25 mg

Example 2: Convert 1.5 mg to mcg

1

mcg = 1.5 × 1,000

2

mcg = 1,500

Answer: 1,500 mcg

Example 3: Convert 75 mcg to mg

1

mg = 75 ÷ 1,000

2

mg = 0.075

Answer: 0.075 mg

When This Converter Is Used

  • •Converting medication doses written in micrograms vs milligrams
  • •Double-checking syringe/ampoule strength vs charted dose
  • •Preventing unit errors (mcg vs mg medication errors)

Clinical safety note: Always verify conversions and follow your facility's protocols. This calculator supports verification but does not replace clinical judgement.

Related Calculators

g ↔ mg

Grams to Milligrams

L ↔ mL

Liters to Milliliters

kg ↔ lbs

Kilograms to Pounds

°C ↔ °F

Celsius to Fahrenheit

Frequently Asked Questions

Clinical reminder: Always follow local protocols and consult medication information sheets. These examples are for calculation practice only.

References & Sources

These sources define SI prefixes and unit conventions used for mcg ↔ mg conversion.

International

BIPM — SI Prefixes (PDF) p.1

Single-page SI prefix chart defining micro (10⁻⁶) and milli (10⁻³).

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United States

NIST — Metric (SI) Prefixes

Official US standards for SI prefix naming and values.

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NIST — The International System of Units (SI) (SP 330 PDF)

Comprehensive SI unit and prefix definitions.

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United Kingdom

NPL (UK) — The SI units

UK National Physical Laboratory SI prefix table.

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NPL (UK) — SI Prefixes (PDF)

2023 SI prefix reference with micro and milli definitions.

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Australia

Australian Government Style Manual — Measurement and units (SI prefixes)

Official Australian government SI prefix conventions.

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Australian legal units — National Measurement Regulations 1999 (Schedule: SI prefixes)

Legal definition of SI prefixes in Australia.

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National Measurement Institute — Australia's measurement system

Official Australian measurement standards and SI conventions.

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