South Georgia and South Sandwich Islands is about 85 times smaller than Vietnam.

Vietnam is approximately 331,210 sq km, while South Georgia and South Sandwich Islands is approximately 3,903 sq km, making South Georgia and South Sandwich Islands 1.18% the size of Vietnam.
Tip: This to-scale comparison of Vietnam 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. Vietnam