An ultra-thin and wideband polarization converting metasurface (PCMS) is presented. This candy shaped metasurface consists of circular patch resonator having square shaped cuts at the two edges and square resonators attached at the diagonals. The PCMS has a single layer dielectric whose thickness and periodicity are, respectively, 2 mm and 7 mm (i.e., $0.08\lambda_{\mathrm{o}}$ and $0.28\lambda_{\mathrm{o}}$ where $\lambda_{\mathrm{o}}$ is the free space wavelength at 12 GHz). The PCMS demonstrates high efficiency polarization conversion ratio (PCR) of more than 90% from 12 to 27 GHz with a bandwidth of 15 GHz and a fractional band-width (FBW) of 77%. To the best of the author's knowledge, the proposed PCMS demonstrate wideband response covering the complete Ku and $\mathrm{K}$ bands. The developed PCMS is ultra-wideband, low profile, light weight, and high efficiency, which makes it a good candidate for applications such as antenna design, radar cross section reduction, microwave and satellite communications.