It depends. Turning off Wi-Fi can save some battery, but usually far less than fixing screen brightness or a weak cellular signal.
Wi-Fi gets blamed for battery drain because it's an always-on radio, but on its own it's usually one of the smaller power draws on a modern phone compared to the display.
Whether turning it off helps at all really depends on what your phone is doing with that connection in the first place.
At home on a strong, stable Wi-Fi connection, the radio sits mostly idle between data requests and uses relatively little power. In that situation, Wi-Fi is often more battery-efficient than cellular data, especially where cell signal is weak.
Most phones show a battery usage breakdown by app and category in Settings. If Wi-Fi or cellular isn't showing up as a top drain, turning it off won't move the needle much, check screen time and specific apps instead.
Airplane mode overnight, or turning off Wi-Fi only when you know you're leaving your usual network range for hours, captures most of the benefit without needing to think about it constantly.
Turning off Wi-Fi helps in specific situations, weak range, no trusted network nearby, but it's rarely the biggest lever for battery life. Check your usage breakdown before assuming it's the fix.
Usually not. Wi-Fi is often more power-efficient than cellular, especially when cell signal is weak, since a weak signal forces the radio to work harder.
It can help slightly, but airplane mode saves more since it also stops cellular and Bluetooth scanning at once.
Phones periodically scan for known or nearby networks in the background, which uses a small, steady amount of power.
Screen brightness, video streaming, GPS navigation, and background app activity are typically bigger drains than Wi-Fi on its own.