South Australia is about 1.4 times smaller than Northern Territory.

Northern Territory is approximately 1,347,791 km² (520,385 sq mi), while South Australia is approximately 984,321 km² (380,048 sq mi), making South Australia 73.03% the size of Northern Territory.
Tip: This to-scale comparison of Northern Territory vs. South Australia 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.