The Android FHD Wallpaper size (1080×1920px)
1080x1920 pixels at 9:16 is the classic Full HD phone resolution and the most universal Android wallpaper size there is. Countless phones ship with or report a 1080-wide FHD panel, and even taller modern devices can use this as a dependable, well-supported baseline, which is exactly why it is the safe choice when you do not know a phone's precise dimensions.
The standard 9:16 shape is a little shorter than the 19.5:9 and 20:9 panels on the newest flagships, so on a very tall phone a 1080x1920 wallpaper may be centered with slight cropping or scaled to fit. On the huge population of true FHD 9:16 phones, though, it fills the screen edge to edge with no distortion, making it ideal as a generic, share-anywhere wallpaper.
Because 1080 pixels wide is plenty sharp for a phone screen, there is little benefit to a much larger source, and this size keeps files light and quick to set as a background. Plan for the interface: most Android lock screens show a clock in the upper area, and home screens fill the lower portion with icons, widgets, and the dock. Keep faces and focal points centered so they survive both the clock overlay and any minor crop on taller phones. This tool resizes entirely in your browser, so your photo is never uploaded, it is free, and your original quality is preserved while the file is fit to the 9:16 frame. Phone specs vary widely, so verify your device.