Last updated: 2026-07-01

Electric charge

Electric charge is the physical property that causes matter to experience a force in an electric field. It is measured as an accumulated quantity: how much charge has flowed past a point, or how much a component can store and deliver. Charge equals current multiplied by time, which is why battery capacities and electronic-component ratings are all expressed in charge units.

Units of electric charge

Coulomb (C) — the SI unit of charge, equal to the charge carried by one ampere of current flowing for one second. One coulomb corresponds to roughly 6.241 × 10¹⁸ elementary charges. It is the base unit for every other charge unit here.

Millicoulomb (mC) — 10⁻³ C. A practical size for charges handled in signal electronics and small capacitors.

Microcoulomb (µC) — 10⁻⁶ C. Common when describing static electricity and the charge stored on small capacitors.

Ampere-hour (Ah) — 3,600 C. The standard rating for battery capacity: one ampere-hour is one ampere of current sustained for one hour. Car, tool, and deep-cycle batteries are usually rated in Ah.

Milliampere-hour (mAh) — 3.6 C. One thousandth of an ampere-hour, and the capacity unit printed on phone, tablet, and small rechargeable batteries.

Key conversion factors

The whole system rests on two exact relationships derived from charge = current × time:

• 1 Ah = 3,600 C (1 A × 3,600 s)
• 1 mAh = 3.6 C (0.001 A × 3,600 s)

From those, 1 Ah = 1,000 mAh, 1 C = 1,000 mC = 1,000,000 µC, and 1 mAh ≈ 277.8 mC.

Worked example

A phone battery is labelled 3,600 mAh. How much charge is that in coulombs and ampere-hours?

1. Convert to ampere-hours: 3,600 mAh ÷ 1,000 = 3.6 Ah.
2. Convert to coulombs: 3.6 Ah × 3,600 C/Ah = 12,960 C. (Equivalently, 3,600 mAh × 3.6 C/mAh = 12,960 C.)

So a 3,600 mAh battery stores 12,960 C of charge. Entering 3600 in the mAh field of the converter shows 3.6 Ah, 12,960 C, 12,960,000 mC, and 1.296 × 10¹⁰ µC.

Charge vs. energy

Charge (measured in Ah or C) is not the same as stored energy. A battery's energy in watt-hours depends on both its charge capacity and its voltage:

• Energy (Wh) = Charge (Ah) × Voltage (V)

Two batteries can hold the same charge in ampere-hours but very different energy if their voltages differ. This converter deals only with charge; when voltage matters, reach for an energy or battery-capacity converter.

Usage

Enter any value in any field. All other units update automatically. For example, type 1000 in the mAh field to see 1 Ah, 3,600 C, 3,600,000 mC, and 3.6 × 10⁹ µC.