Electric Charge Conversion Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/10/2026
To convert an electric charge, it is reduced to the coulomb (the SI base unit), then converted into the new unit. One ampere-hour equals exactly 3,600 coulombs, so a 2,000 mAh battery (a common capacity) equals 7,200 coulombs.
Explanation
Electric charge measures the total amount of electricity that has flowed, and comes in several units depending on the context of use. The coulomb (C), the SI base unit, is defined as the charge carried by a one-ampere current for one second — a unit rarely used directly in everyday life because it represents a fairly large amount of charge for domestic purposes. The ampere-hour (Ah) and its submultiple the milliampere-hour (mAh), by contrast, are ubiquitous in characterizing batteries and cells: they indicate how long a device can supply a given current before running down (a 2,000 mAh battery can, for example, supply 2,000 mA for about one hour, or 1,000 mA for about two hours, in a simplified approximation that ignores real non-linear discharge effects). The conversion factor between ampere-hour and coulomb (exactly 3,600) follows directly from the definition of the hour in seconds, exactly as the time conversion between hours and seconds rests on that same definition — these are not measured values but exact arithmetic consequences of the unit definitions themselves.
Example: converting an AA cell capacity to coulombs
Inputs
Value: 2,000. Starting unit: milliampere-hours. Target unit: coulombs.
Calculation
2,000 mAh × 3.6 (factor from mAh to C) = 7,200 C.
Result
A 2,000 mAh battery, a common capacity for a rechargeable AA cell, holds a total electric charge of about 7,200 coulombs.
Frequently asked questions
Why are battery capacities rarely expressed in coulombs?
Because the coulomb represents a fairly large amount of charge relative to the practical needs of a typical electronic device: expressing a small battery's capacity in coulombs would give numbers that are unintuitive to handle day to day. The ampere-hour (and especially its submultiple the milliampere-hour) has the advantage of relating directly and intuitively to a device's practical run time, which is why it is nearly universal on cell packaging and battery data sheets.
Does the mAh capacity directly give a device’s real run time?
Only approximately: dividing the capacity in mAh by the device's consumption in mA gives a simplified estimate of run time in hours, but reality is more complex. A battery's actually available capacity varies with the discharge current (a very fast discharge generally reduces the effective capacity compared with a slow one), ambient temperature, and battery age — so this conversion gives a theoretical order of magnitude, not a guaranteed run-time prediction under all conditions.
What is the difference between the ampere-hour and the watt-hour?
The ampere-hour measures an amount of electric CHARGE, independent of the battery's voltage, while the watt-hour (Wh) measures an amount of ENERGY — the same relationship between current, voltage, and electric power covered elsewhere on this site (Wh = Ah × voltage in volts). Two batteries with the same Ah capacity but different voltages (for example 1.2 V for a NiMH cell versus 3.7 V for a lithium-ion battery) therefore store very different amounts of energy despite an identical Ah capacity.