Calculate mAs from milliamps and exposure time, adjust mAs for distance changes, and apply the 15% kVp rule for radiography settings.

mAs Calculator

Basic mAs
Distance compensation
kVp/mAs 15% rule

Enter any 2 values to calculate the missing variable

mAs Formula

The following formula is used to calculate Milli-ampere-seconds (mAs). 

mAs = mA * t
  • Where mAs is milliampere seconds
  • mA is total milliamps
  • t is total time (s)

To calculate milliampere seconds (mAs), multiply the Milli-amps by the time in seconds.

mAs Definition

What is mAs?

mAs is a unit of measure that is equal to one milliamp times one second. This unit of measure is most often used in the study of radiology to depict how much radiation is produced over a set amount of time.

Example Problem

How to calculate mAs?

  1. First, determine the total milliamps the x-ray is producing.

    For this example, the x-ray is emitting 300 milliamps (mA).

  2. Next, determine the total time the radiation is being emitted.

    In this case, the x-ray takes a total time of .03 seconds.

  3. Finally, calculate the mAS.

    Using the formula above, the mAs is calculated to be:
    mAs = mA * t
    mAs = 300 *.03
    mAs = 9