South Georgia and South Sandwich Islands is about 15 times bigger than Niue.

Niue is approximately 260 sq km, while South Georgia and South Sandwich Islands is approximately 3,903 sq km, making South Georgia and South Sandwich Islands 1,401% larger than Niue.
Tip: This to-scale comparison of Niue vs. South Georgia and South Sandwich Islands uses the Mercator projection, which distorts the size of regions near the poles.
Compare further: South Georgia and South Sandwich Islands vs. Niue