femtoliters

A femtoliter (symbol fL; or femtolitre in British usage) is a unit of volume equal to 10^-15 liters. In practical terms, a femtoliter is the same as a cubic micrometer (μm^3): 1 fL = 1 μm^3. This equivalence arises because 1 μm is 10^-6 meters, and cubing gives 10^-18 m^3, which converts to 10^-15 liters when expressed in liters.

In scale terms, femtoliters describe volumes at the cellular to microfluidic level. A typical mammalian cell has a volume on the order of about 1,000 fL, while a bacterial cell such as E. coli is roughly 1–3 fL. By comparison, 1 picoliter (pL) equals 1,000 fL, and 1 microliter (μL) equals 10^9 fL. These relationships help place fL within the broader metric hierarchy of liquid volumes.

Applications of the femtoliter scale are common in biology and nanotechnology, particularly in microfluidics and single-molecule assays. Researchers describe reaction chambers, droplets, and assay volumes in the fL to pL range, enabling high-throughput screening, digital PCR, and nucleic acid sequencing workflows. The precise handling of such small volumes requires specialized equipment, including microfluidic devices, nanoliter or picoliter dispensers, and careful calibration.

See also: SI units of volume, microliter, picoliter, nanoliter.