Abstract: A coating thickness gauge employs a permanent magnet suspended on a coil spring within a pencil shaped housing; the spring being attached to a slide which encircles the housing aid is manually slidable along the length of the housing to adjust the tension of the spring exerted on the magnet. The end of the magnet projects through the end of the housing in contact with a coating deposited on a ferromagnetic base so that the thickness of the coating is measured in terms of the spring tension exerted when the side is moved to pull the magnet away from the coating and this thickness can be read on a scale mounted along the length of the housing. The slide can be provided with internal resilient friction rings or an internal expandable friction element can be placed in the housing to resist inadvertent movement of the slide and an internal stop can be employed to prevent bouncing of the magnet to displace the slide.