Calculate radiographic mAs, tube current, or exposure time, compensate mAs for SID changes, and estimate 15% kVp rule adjustments with clear safety notes.

Calculation mode

What do you want to find?

Tube current (required)

Exposure time (required)

Educational calculation only. mAs is not patient dose. Verify selections against equipment limits, approved technique charts, detector guidance, patient factors, AEC behavior, and local radiation-safety protocols.

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?

First, determine the total milliamps the x-ray is producing.
For this example, the x-ray is emitting 300 milliamps (mA).
Next, determine the total time the radiation is being emitted.
In this case, the x-ray takes a total time of .03 seconds.
Finally, calculate the mAS.
Using the formula above, the mAs is calculated to be:
mAs = mA * t
mAs = 300 *.03
mAs = 9