This document summarizes stress in a bar with a uniformly tapering rectangular cross section. It defines the width of the larger and smaller ends (b1 and b2), length (L), thickness (t), and modulus of elasticity (E). It describes how to calculate the cross-sectional area (A) as a function of position (x), tensile stress (σ), and total elongation or extension (δL) of the bar when an axial pull force P is applied. As an example, it gives values to calculate the extension of a steel plate that tapers from 200mm to 100mm width over 500mm length, under an axial force of 40kN.