Petagram to Femtogram

The femtogram is a unit of mass equal to 10⁻¹⁵ grams or 10⁻¹⁸ kilograms — one quadrillionth of a gram.

1 fg = 10⁻¹⁵ g = 10⁻¹⁸ kg = 1,000 ag.

To convert fg to kg: multiply by 10⁻¹⁸. To convert fg to pg: divide by 1,000.

Expressing the mass of individual bacterial cells (~100 fg for E. coli) and subcellular components.

A single E. coli bacterium has a mass of about 600–700 fg. A single mitochondrion is roughly 1 fg.

Mixing up fg (femtogram) with fm (femtometer) — one is mass, the other is length.

A bacterium weighs ~500 fg — this gives you a tangible anchor for the femtogram scale.