The present invention relates to an indexable cutting insert for an end mill for machining of contours in a workpiece and to a milling tool. The cutting insert is asymmetrical in respect of a line through a hole in the cutting insert. The cutting insert comprises two cutting edge portions. Each cutting edge portion comprises a substantially straight cutting edge and a curved cutting edge along respective intersecting lines between a clearance surface and a rake face. The curved cutting edges have different lengths. The cutting insert has a bottom side and a first and a second opposite corner. The second corner is defined in plane view by a radius that is greater than, preferably at least twice as great as a radius of the first corner.