South Georgia and South Sandwich Islands is about 2.9 times smaller than Gambia.

Gambia is approximately 11,300 sq km, while South Georgia and South Sandwich Islands is approximately 3,903 sq km, making South Georgia and South Sandwich Islands 34.54% the size of Gambia.
Tip: This to-scale comparison of Gambia 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. Gambia