We have reports of up to 50-feet distance two story house without needing WiFi extenders. For longer distance, the 2.4Ghz channel works better. The number of walls between the router and the device plays a big role. But usually the signal strength is a good indicator (check the Status page, need to be >-80dBm to get decent transmission speed).
Picking the right channel is important if there are a lot of WiFi signals around your house. On the far end, your neighbor’s signal might be stronger than yours. Please check out this post: https://www.pcwrt.com/2017/10/how-to-avoid-bad-wifi-connection-by-changing-the-channel-on-your-router/.
