Attoliters

Attoliter (symbol aL) is a unit of volume in the International System of Units (SI), equal to 10^-18 liters. The prefix atto- denotes 10^-18, placing attoliters between zeptoliters (10^-21 L) and femtoliters (10^-15 L) on the metric scale. In practical terms, attoliters describe extremely small volumes.

One attoliter equals 1×10^-18 liters, and in cubic meters it is 1×10^-21 m^3. In other common units, 1 aL is 0.001 femtoliters, or 1×10^-6 picoliters, and 1×10^-12 microliters. Because of their tiny size, attoliters are rarely used in routine measurements, with nanoliters, picoliters, and microliters serving most laboratory needs. They may appear in discussions of microfluidics, nano-scale experiments, or theoretical considerations of extremely small sample volumes.

As a rough spatial reference, a sphere with a radius of about 62 nanometers has a volume near 1 aL, corresponding to a diameter of roughly 124 nanometers. This illustrates why attoliters are associated with nanoscale structures and technologies rather than everyday laboratory volumes.

The attoliter is one of several SI volume units derived from the atto- prefix, used to express very small quantities of liquid. It reinforces how SI prefixes enable precise communication across a wide range of magnitudes, from inches to liters and beyond.