Electric Charge Converter

Electric charge is the quantity of electricity itself, the thing that current carries along. The SI unit is the coulomb (C): one ampere flowing for one second moves one coulomb. For everyday electronics, though, the unit that actually matters is the ampere-hour, because that’s how battery capacity is sold.

Metric prefixes:

• 1 C = 1,000 mC (millicoulombs)
• 1 C = 1,000,000 µC (microcoulombs)

Ampere-hour units:

• 1 Ah = 3,600 C (one amp for one hour)
• 1 mAh = 3.6 C

Real-world charges:

• A phone battery: 3,000–5,000 mAh
• A car battery: 40–100 Ah
• A lightning bolt: about 5 C

The phone-to-car gap is bigger than it looks. A 4,000 mAh phone holds 4 Ah; a 60 Ah car battery holds fifteen times the charge, at a much higher voltage on top of that.

And that voltage point is the real trap: charge is not energy. A 5,000 mAh power bank and a 5,000 mAh phone cell do not store the same usable energy if they run at different voltages, because energy in watt-hours is charge times voltage. Comparing battery capacities in mAh across devices with different voltages tells you almost nothing. When you actually want to know what a battery can do, convert to watt-hours first, which is what the voltage dropdown above is for: pick the cell chemistry and the page multiplies it out.

The lightning figure is the one worth sitting with. Five coulombs sounds enormous next to a microcoulomb of static, but a 4,000 mAh phone battery holds 14,400 coulombs, close to three thousand strokes’ worth. Lightning is dangerous because it delivers its charge in a few microseconds at something like a hundred million volts, not because the quantity of charge is large. Charge tells you how much; voltage and time tell you what it does.

Counted as particles, one coulomb is 6.24 x 10^18 electrons, because a single electron carries 1.602176634 x 10^-19 coulombs. That figure has been exact by definition since the SI was redefined in 2019, so the ampere is now built on the electron rather than the other way around.