Pressure vessels are held together against the gas pressure due to tensile forces within the walls of the container. The normal tensile stress in the walls of the container is proportional to the pressure and radius of the vessel and inversely proportional to the thickness of the walls.

Pressure vessels a given pressure the thickness of the walls scales with the radius of the tank, the mass of a tank which scales as the length times radius times thickness of the wall for a cylindrical tank scales with the volume of the gas held which scales as length times radius squared.

The exact formula varies with the tank shape but depends on the density, ρ, and maximum allowable stress of the material in addition to the pressure P and volume V of the vessel. Pressure vessels below for the exact equations for the stress in the walls.Therefore pressure vessels are designed to have a thickness proportional to the radius of tank and the pressure of the tank and inversely proportional to the maximum allowed normal stress of the particular material used in the walls of the container.