picograms

A picogram is a unit of mass in the metric system equal to one trillionth of a gram. Its symbol is pg, and it represents 1 × 10^-12 g. In SI base units, a picogram is 1 × 10^-15 kilograms. It sits between the nanogram (10^-9 g) and the femtogram (10^-15 g) on the scale of very small masses.

The picogram is commonly used in biology, chemistry, and related fields to describe extremely small amounts of material. In practical terms, many biological molecules fall into the picogram to nanogram range, making the picogram a convenient reference for quantitative measurements. For example, the mass of a human haploid genome is about 3.3 pg; the mass of a typical diploid human genome is about 6.6 pg.

Conversions to other units are straightforward: 1 ng equals 1000 pg; 1 μg equals 1,000,000 pg; 1 mg equals 1,000,000,000 pg; 1 g equals 1,000,000,000,000 pg. Because quantities at the picogram scale are very small, specialized equipment and techniques—such as high-precision balances and sensitive analytical methods—are often required to measure and work with such masses accurately.

Picograms are thus a practical unit for reporting trace quantities of DNA, RNA, proteins, and other biomolecules, reflecting the need to quantify materials that are far too light to be measured in larger units.