By Chris Deziel Updated Aug 30, 2022
Electricity is the flow of electrons—tiny, negatively charged particles that orbit every atom. The unit of current, the ampere, is defined as one coulomb of charge passing through a point per second. To translate that into the number of electrons, we simply need the elementary charge: 1.602 × 10⁻¹⁹ coulombs per electron.
One ampere carries 6.242 × 10¹⁸ electrons each second. Multiply your current value by this factor to find the electron flow rate.
The coulomb (C) is the SI unit of electric charge. It is defined as the total charge that flows through a conductor in one second when the current is one ampere. Although the coulomb was originally derived from the statcoulomb in the CGS system, modern physics defines it directly through the ampere.
In 1909, American physicist Robert Millikan used charged oil droplets between two electrodes to measure the fundamental unit of charge. By balancing gravitational and electric forces, he determined that all observed charges were integer multiples of 1.602 × 10⁻¹⁹ C—the charge of a single electron. This experiment earned Millikan the Nobel Prize in Physics.
Since one electron carries 1.602 × 10⁻¹⁹ C, the reciprocal gives the number of electrons per coulomb:
1 C = 6.242 × 10¹⁸ electrons
Because 1 A equals 1 C / s, we have:
1 A = 6.242 × 10¹⁸ electrons per second
The conversion factor above allows you to translate any current into an electron count. For example:
Use this simple formula whenever you need to estimate particle flow in electrical circuits.
