Abstract: This invention describes a pressure gauge which is one embodiment is adapted to be continuously mounted on the valve stem of the inflated device, thereby providing a continuous indication of the pressure therein. It includes an airtight enclosure formed by an expandable means such as a diaphragm, positioned within an outer housing. The gauge is adapted to contact the standard valve stem in the inflated device to release pressurized gas from the device into the airtight enclosure. In response thereto, the airtight enclosure expands. Cooperating with this expansion of the airtight enclosure is a piston like member which includes means for controlling the expansion of the airtight enclosure. The control means is calibrated so that the piston like member moves an axial distance in an amount proportional to the pressure of the gas in the tube. The piston has an indicator band painted thereon which positions itself opposite appropriate psi markings on the outside of the housing.