Milliampere-second (mAs) is an x-ray unit determined by multiplying the milliamperes by the time the x-ray tube is generating x-rays. On many x-ray machines this is a technique factor selected by the operator that together with kVp determines the exposure of patient and image receptor.[1]


If you want to calculate the mAs, you multiply mA x s = Milliamp-second (mAs)

Let's pretend you have a technique setup to take a shot at 200 miliamps (mA) at a timing of .25 second (1/4 sec).

For example: mA = 200, s = 0.25 1. (200 x 0.25) 2. mAs = 50 mAs 3. Answer = 50mAs


  1. Conference of Radiation Control Program Directors, Inc. "COMPUTED RADIOGRAPHY (CR) AND DIGITAL RADIOGRAPHY (DR) STATE X-RAY INSPECTION PROTOCOL--Publication No. E-10-2 " Jan 2010.