Electric Charge converter

The coulomb is the base unit of electric charge, and most of the units here are either decimal multiples of it (kilocoulomb, millicoulomb, microcoulomb, nanocoulomb, picocoulomb) or practical battery-rating units built from current × time, since charge is exactly that: the ampere-hour and milliampere-hour. A handful of legacy units — the abcoulomb, statcoulomb, faraday, and elementary charge — come from older or more specialized measurement systems, but every one of them ultimately reduces to a fixed multiple of the coulomb.

To convert milliampere-hours to coulombs, multiply by 3.6:

C = mAh × 3.6

A typical smartphone battery rated at 3,000 mAh therefore stores 3,000 × 3.6 = 10,800 coulombs of charge. Scale that up to a power-tool battery rated at 2 Ah (2,000 mAh): 2 × 3,600 = 7,200 coulombs. And at the opposite end of the scale, a single coulomb corresponds to about 6.242 × 10¹⁸ electrons (1 ÷ 1.602176634×10⁻¹⁹), a constant worth knowing any time you need to connect a macroscopic charge measurement, like a battery rating or a lightning strike's charge transfer, to a literal electron count.

Charge units show up constantly outside the physics classroom: every battery capacity rating on a phone, laptop, power bank, or electric vehicle is quoted in Ah or mAh, which is a charge figure even though shoppers often read it as a proxy for "how much energy" the battery holds. Electrochemists lean on the faraday constant to calculate exactly how much metal gets deposited or dissolved during electroplating and electrolysis, since Faraday's laws of electrolysis relate charge passed directly to moles of substance reacted — critical for anything from silver-plating jewelry to refining aluminum at industrial scale. Particle and semiconductor physicists, meanwhile, often work in multiples of the elementary charge itself rather than converting to coulombs at all, since that's the natural unit for describing the charge carried by a single electron, proton, or ion. Even atmospheric scientists use coulombs when describing how much charge a lightning strike transfers between a cloud and the ground, typically tens of coulombs in a fraction of a second.

One subtlety worth flagging: a battery's mAh rating is charge, not energy, so two batteries with the same mAh rating but different voltages store different amounts of usable energy (energy = charge × voltage) — that's why watt-hours, not amp-hours, are the fair way to compare batteries across different voltage classes, and why comparing a 3.7 V phone cell to a 12 V power-tool pack purely by mAh rating is misleading. It's also easy to confuse the faraday (a unit of charge, about 96,485 C, used in electrochemistry) with the completely unrelated farad (a unit of capacitance, used for capacitors) — same root name, honoring the same scientist, but entirely different physical quantities measuring entirely different things. A smaller but similar trap sits between the abcoulomb and the ordinary coulomb: the abcoulomb's factor of 10 is easy to mistake for a typo or a simple metric multiple, when it's actually a fixed artifact of how the older CGS-EMU system defined its base electrical units relative to length, mass, and time rather than relative to the modern ampere.