Flathead Lake is around the same size as Lake Tahoe.

Lake Tahoe is approximately 502 km² (194 sq mi), while Flathead Lake is approximately 510 km² (197 sq mi), making Flathead Lake 2% larger than Lake Tahoe.
Tip: This to-scale comparison of Lake Tahoe vs. Flathead Lake uses the Mercator projection, which distorts the size of regions near the poles.
Our free app, MapSize by MyLifeElsewhere — compare any two places, to scale on your mobile device.