Paint thickness can be measured using a variety of methods, including:

Magnetic pull-off

A permanent magnet and calibrated spring pull together, and the force required to separate them is measured. Thinner coatings have a stronger magnetic attraction.

Ultrasonic

A probe touches the coating, and an ultrasonic wave is transmitted toward the base. The time it takes for the wave to reflect back is used to calculate the thickness.

Infrared

Infrared light is shone on the coating, and the absorption of specific wavelengths is measured. The thickness is calculated based on the relationship between the absorption rate and the material’s thickness.

Paint thickness is commonly measured in mils or microns:

Mils: In the US, one mil is equal to 1/1000 of an inch.

Microns: In the metric system, one micron is equal to 1/1000 of a millimeter. To convert mils to microns, multiply the number of mils by 25.4. To convert microns to mils, divide the number of microns by 25.4.