Question: 4k equals how many megapixels?
Answer: That 3840 × 2160 works out to 8.3 megapixels, the official resolution of 4K UHD (and therefore Blu-ray UHD discs). The 4K UHD standard does not specify how large the pixels are, so a 4K UHD projector (Optoma, BenQ, Dell, et al.) counts because these projectors have a 2718 × 1528 pixel structure.