Maui is about 1.2 times bigger than Oahu.

Oahu is approximately 1,545 km² (597 sq mi), while Maui is approximately 1,883 km² (727 sq mi), making Maui 22% larger than Oahu.
Tip: This to-scale comparison of Oahu vs. Maui 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.