Electric Charge Converter Calculator
Convert between all common electric charge units. From coulombs for physics to ampere-hours and milliampere-hours for battery capacity, this converter handles charge units across electrical engineering, chemistry, and fundamental physics.
Understanding Electric Charge Units
Electric charge is a fundamental property of matter that causes it to experience electromagnetic force. The SI unit of charge is the coulomb (C), defined as the charge transported by one ampere of current flowing for one second. A single lightning bolt transfers about 5 coulombs of charge, while static electricity from shuffling across carpet involves microcoulombs.
The ampere-hour (Ah) and milliampere-hour (mAh) are practical charge units for batteries and electronics. One Ah equals 3,600 coulombs. Battery capacity in Ah tells you how long a battery can sustain a given current. A 100 Ah car battery can theoretically deliver 5 amps for 20 hours, though actual capacity varies with discharge rate and temperature.
The elementary charge, about 1.602 x 10^-19 coulombs, is the smallest freely observable unit of charge. All macroscopic charges are integer multiples of this value. The Faraday constant, about 96,485 coulombs per mole, connects charge to chemistry by specifying how much charge is carried by one mole of electrons, making it essential for electrochemistry calculations.
Electric Charge in Battery Technology
Consumer electronics rate batteries in milliampere-hours. A smartphone with a 4,500 mAh battery at 3.8 volts stores about 17.1 watt-hours of energy. Larger devices like laptops specify capacity in watt-hours directly (typically 50-100 Wh) because their multi-cell battery packs operate at different voltages than individual cells.
Electric vehicle batteries are rated in kilowatt-hours rather than ampere-hours because the pack voltage varies between manufacturers. A 75 kWh Tesla battery pack contains about 1,000 Ah at its nominal voltage of 75 volts. Converting between Ah and kWh requires knowing the system voltage, which differs across battery chemistries and configurations.
Battery charging involves moving charge back through the cell. A fast charger delivering 3 amps to a 3,000 mAh phone battery takes about one hour theoretically, but charging curves are not linear. The final 20% of charge takes longer to protect battery health. Understanding charge units helps consumers evaluate charging claims and compare battery specifications across devices and brands.
Electric Charge in Physics and Chemistry
Electrochemistry uses the faraday constant to predict how much material is deposited during electrolysis. To deposit one mole of copper from solution requires two faradays of charge (about 193,000 coulombs) because copper ions carry a +2 charge. This calculation is fundamental to electroplating, metal refining, and battery design, and it requires consistent charge unit usage.
Capacitors store charge on their plates, with capacitance measured in farads (coulombs per volt). A 1-farad capacitor charged to 5 volts stores 5 coulombs. Supercapacitors can store hundreds of farads, bridging the gap between traditional capacitors and batteries for energy storage applications that need rapid charge and discharge cycles.
Particle physics measures charge in elementary charge units. Quarks carry fractional charges of +2/3 or -1/3 of an elementary charge, but they are never observed in isolation. The electron's charge was first measured by Robert Millikan in his oil drop experiment, yielding a value remarkably close to the modern accepted value of 1.602176634 x 10^-19 coulombs, now defined as an exact value in the SI system.
Frequently Asked Questions
How do I convert ampere-hours to coulombs?
Multiply ampere-hours by 3,600 to get coulombs, since one hour equals 3,600 seconds and one ampere is one coulomb per second. A 5 Ah battery stores 18,000 coulombs of charge. Going the other direction, divide coulombs by 3,600 to get ampere-hours.
What is a milliampere-hour?
A milliampere-hour (mAh) is one thousandth of an ampere-hour. It is the standard unit for smartphone and small battery capacity. A typical smartphone battery holds 3,000-5,000 mAh, meaning it can deliver 3,000-5,000 milliamps for one hour, or proportionally less current for longer times.
What is a faraday of charge?
One faraday equals approximately 96,485 coulombs and represents the charge of one mole (6.022 x 10^23) of electrons. It is used in electrochemistry to calculate how much charge is needed to deposit or dissolve a given amount of material during electrolysis.
What is an elementary charge?
The elementary charge is the electric charge of a single proton (or the magnitude of an electron's charge): approximately 1.602 x 10^-19 coulombs. It is the fundamental quantum of electric charge in nature. All observable charges are integer multiples of this value.
How does battery capacity in mAh relate to energy?
Battery capacity in mAh tells you charge, not energy. To get energy in watt-hours, multiply mAh by voltage and divide by 1,000. A 5,000 mAh battery at 3.7 volts stores 18.5 Wh of energy. Two batteries with the same mAh but different voltages store different amounts of energy.