Metric (SI)SI Ratio: 1e-9 kg

Microgram (µg)

A microgram is equal to one-millionth of a gram (10⁻⁶ g) or one-billionth of a kilogram (10⁻⁹ kg).

Definition & Scientific Metrology

Also abbreviated as "mcg" in medical records to avoid confusion with mg. It is vital for hormones, potent pharmaceuticals, and environmental pollutants.

SI Kilogram Base Factor

1 µg = 1e-9 kg

Origins & Historical Evolution

Standardized by the BIPM using the Greek letter µ (mu) representing 10⁻⁶.

1 Microgram in Other Mass Units

Direct standard conversion equivalents for 1 µg:

Target Unit	Equivalent Value	Multiplier Equation
Milligrams (mg)	0.001	`1 µg × 0.001`
Grams (g)	0	`1 µg × 0.000001`
Kilograms (kg)	0	`1 µg × 1e-9`

Common Real-World Applications

Thyroid medication (Levothyroxine)
Vitamins such as Vitamin B12, Vitamin D, and Folic Acid
Air particulate pollution monitoring (PM2.5 concentration in µg/m³)

Did You Know?

Interesting Metrology Facts

💡

A human egg cell (ovum) weighs approximately 1 microgram.

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A fingerprint left on a surface has a mass of only a few micrograms.

Measurement Standards & Accuracy

Standard Multipliers

Factors based on the 1959 International Yard and Pound Agreement and NIST SP 811.

Sources

BIPM International Metrology Treaty
NIST Guide for SI Units
ISO 80000-4 Quantities and Units — Mass

Accuracy & Policy

Standard Exact Multipliers (e.g., 1 lb = 0.45359237 kg)

Reviewed: October 2026 • About our methodology →

Related Tools & Resources for Microgram

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