Photosynthetic Photon Flux (PPF) is the metric used to measure PAR. It is a total count of light energy (in photons) from 400nm to 700nm.
PPF is measured in micromols (μmol). Micromols are 10-6 of a mol (A mol is a unit of measurement). The measurement is classified in time, revealing how many seconds it takes the light to reach the measurement tool. PPF is expressed as μmol/sec.
The calculation for PPF is: