Abstract: A method for determining the volume a substance having a density level in vertical storage tanks. This method uses a strain gauge that is attached to the exterior of the side wall of a tank. As the volume of the substance fluctuates in the tank, the walls are acted upon by the weight of the substance. The greater the volume of a substance, the greater the force pushing on the tank walls and vice-versa. This force causes the walls to deform slightly. This deformation can be measured by the strain gauge mounted on the tank wall. Because this deformation is directly related to the volume of the substance being stored in the tank, the deformation read by the strain gauge can be translated into its volume by calibrating the gauge measurements with known volumes in the tank.