A simple technique is presented for determining the size of the Dugdale plastic zone in two-dimensional edge crack problems. The technique employs a representation from which the weight function may be derived, and the only data required are a single elastic stress intensity factor calibration for the geometry of interest and the elastic stress field in the uncracked body. At most three numerical quadratures provide sufficient information to specify the coefficients in an algebraic expression for the plastic zone size. The technique is illustrated for the examples of edge cracks in semi-infinite sheets, tensile strips, curved beams, and cracked rings. Numerical results agree with existing solutions.