Northern Territory is about 1.9 times smaller than Western Australia.

Western Australia is approximately 2,527,013 km² (975,685 sq mi), while Northern Territory is approximately 1,347,791 km² (520,385 sq mi), making Northern Territory 53.34% the size of Western Australia.
Tip: This to-scale comparison of Western Australia vs. Northern Territory uses the Mercator projection, which distorts the size of regions near the poles.
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