Put simply, download speed is how quickly your Internet connection can retrieve data from the Internet (web pages, video, cat photos, etc.) and upload speed is how quickly your Internet connection can send data from your devices up to the Internet (uploading video to YouTube, sending documents via email, etc.) Netflix recommends at least a 5 Mbps download speed for standard HD video, and a 25 Mbps download speed for 4K content. However, it’s important to keep in mind that these numbers refer to what the service on its own needs — not the total speed of your Internet plan.
For instance, say you have a 25 Mbps down connection speed. If the total capacity of your Internet connection is a pie, you can imagine that every user on the network (and all of their various devices) each get a “slice” of that pie. Essentially, your total potential speed is split across all of the devices connected to the network, so that 25 Mbps may only be providing 10-15 Mbps to Netflix itself, preventing you from streaming 4K content smoothly. Also, using Wi-Fi will always be a bit slower than a hardwired connection. To ensure that you’re maximizing your chances of a trouble-free streaming experience try to position the streaming device as close to the router as possible, with no physical barriers like walls or furniture between them. This will help you achieve a more stable connection.
To better determine the speed you need, take an accurate count of the all the devices in your home, and what they are being used to do, then go to the TCT website and take the Speed Calculator test. This should give you an idea of what speed you will need for your home and your family. https://tctelco.net/broadband-decider/