The stress intensity factors for arbitrarily shaped cracks in an infinite two-dimensional elastic medium were investigated. The conformal map was constructed from the exterior of the unit circle to exterior of the arbitrary crack using the method of iterated conformal maps. The method, when compared with the Schwartz-Cristoffel transformation, was found to be better. The conformal method allowed an accurate estimate of the stress intensity factors or of the subleading terms such as the T-stress and simplified the calculation of the full stress field.