About the Coulombs to Ah Converter
Coulombs are the scientific unit of electric charge, while batteries are sold in amp-hours and milliamp-hours. This converter turns coulombs into amp-hours by dividing by 3,600, because one amp for one hour moves 3,600 coulombs. Type the charge in coulombs and read the amp-hours at once, with milliamp-hours, millicoulombs, microcoulombs and elementary charges listed below. It is helpful when a textbook problem or an electrolysis calculation gives charge in coulombs and you want to compare it with a real battery, or when a lab measurement of charge needs to be expressed in the unit used on a battery label. It runs in your browser and nothing is uploaded.
Updated October 2026
How to use the Coulombs to Ah Converter
- 1Type the electric charge in coulombs.
- 2Read the amp-hours (Ah) at the top.
- 3See milliamp-hours and the other units in the rows below.
- 4Press Copy to copy the sentence, for example 9000 C = 2.5 Ah.
- 5Change the number for another value.
The formula
amp-hours = coulombs ÷ 3,600. The factor comes from 60 seconds in a minute and 60 minutes in an hour.
To go the other way, multiply by 3,600 with the Ah to Coulombs converter.
Examples
- 3,600 C = 1 Ah
- 1,800 C = 0.5 Ah = 500 mAh
- 36,000 C = 10 Ah
- 1 C = 0.2778 mAh
A worked example
Suppose an electrolysis experiment passes 54,000 coulombs through a cell. Dividing by 3,600 gives 15 Ah, which is the same as running 5 A for 3 hours. Knowing it in amp-hours makes it easy to picture, and a lab power supply set to 5 A would need 3 hours to supply that charge.
The same quantity of charge in elementary charges is about 3.37 × 10^23, close to half of a mole of electrons since the Faraday constant is about 96,485 C per mole.
Capacity and runtime
A battery's amp-hour rating tells you how long it can supply a given current. Divide the amp-hours by the current in amps to estimate the hours. Real runtime is shorter when the current is high, the battery is cold or it is old, so treat the figure as a guide.
Common questions about charge
Students often meet coulombs in problems that give a current and a time: charge is current times time, so 2 A for 30 minutes is 3,600 C, which is exactly 1 Ah. Going the other way, a charge in coulombs divided by the time in seconds gives the average current.
Remember that coulombs do not say how much energy was moved. Pair the charge with a voltage to get joules, or use the Volts to Joules Calculator.
Phone and computer
The result updates as you type and sits under the input on a phone, beside it on a computer. For the reverse step, use the Ah to Coulombs Converter, and for the energy in a cell, the mAh to Wh Calculator.
Features
- Exact factor: 3,600 coulombs per amp-hour
- Milliamp-hours, millicoulombs and microcoulombs shown
- Elementary charges for physics work
- Ten significant digits
- Copy button
- Works in your browser
Frequently asked questions
How many amp-hours are in one coulomb?
One coulomb is 1 divided by 3,600 of an amp-hour, about 0.000277778 Ah or 0.2778 mAh.
How do I convert coulombs to amp-hours by hand?
Divide the coulombs by 3,600. For example 7,200 C is 2 Ah.
How do I get milliamp-hours?
Divide by 3.6. So 10,800 C is 3,000 mAh, a typical phone battery.
What is a coulomb?
A coulomb is the charge carried by a current of one ampere in one second. It is about 6.241509 × 10^18 elementary charges.
Does charge tell me the energy stored?
Not alone. Energy in joules equals charge in coulombs times voltage, so a battery's energy depends on both.
Why are batteries rated in Ah, not coulombs?
Hours are a more natural unit than seconds for batteries that last for hours, and amps are what a meter reads.
Is my number sent anywhere?
No. It stays in your browser.