Abstract: This invention is directed to a window shade cutter for manually trimming the end of a rolled shade to conform to the size of the window opening into which the shade is to be mounted. The cutter includes a cylindrical clamping sleeve, having an annular guide groove at one end thereof, adapted to slip over the shade and clamp in place and a cutoff tool receivable in the guide groove including a generally planar U-shaped holder and a planar blade mounted on the holder. In a preferred form, the blade has a rounded, dull end with a central V-shaped notch therein in which a pair of cutting edges are located. The cutoff tool is adapted to interlock in the guide groove and to rotate about the shade with cutting of the shade taking place in the V-shaped notch a few layers at a time as the tool is urged towards the shade and rotated. In accordance with the invention disclosed, window shades can be safely and easily trimmed by the consumer in the home thus eliminating the need for cutting machines.