Christmas Island is about 3 times smaller than Heard Island and McDonald Islands.

Heard Island and McDonald Islands is approximately 412 sq km, while Christmas Island is approximately 135 sq km, making Christmas Island 32.77% the size of Heard Island and McDonald Islands.
Tip: This to-scale comparison of Heard Island and McDonald Islands vs. Christmas Island uses the Mercator projection, which distorts the size of regions near the poles.

Compare further: Christmas Island vs. Heard Island and McDonald Islands

Our free app, MapSize by MyLifeElsewhere — compare any two places, to scale on your mobile device.