It is hard to say exactly how many words are needed for a 3-minute English video. It depends on the content of the video, the speed at which it is spoken, and other factors. For example, if the video features a narrator speaking slowly and clearly about a simple topic, fewer words may be needed than if it contains complex information that is spoken quickly. On average, however, one can expect to need around 300-500 words for a 3-minute English video.