An ampere-hour or amp-hour (symbol Ah , A·h, A h) is a unit of electric charge, with sub-units milliampere-hour (mAh) and milliampere second (mAs). One ampere-hour is equal to 3,600 coulombs (ampere-seconds), the electric charge transferred by a steady current of one ampere for one hour.^[1] The ampere-hour is frequently used in measurements of electrochemical systems such as electroplating and electrical batteries. The commonly seen milliampere-hour (mAh or mA·h) is one-thousandth of an ampere-hour (i.e., 3.6 coulombs).

A milliampere second (mAs or mA·s) is a unit of measure used in X-ray diagnostic imaging and radiation therapy. This quantity is proportional to the total X-ray energy produced by a given X-ray tube operated at a particular voltage.^[2] The same total dose can be delivered in different time periods depending on the X-ray tube current.

The Faraday constant is the charge on one mole of electrons and is approximately equal to 26.8 ampere-hours, and is used in electrochemical calculations.

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