Canberra is about 1.8 times bigger than Antigua and Barbuda.

Antigua and Barbuda is approximately 443 sq km, while Canberra is approximately 814 sq km, making Canberra 84% larger than Antigua and Barbuda.
Tip: This to-scale comparison of Antigua and Barbuda vs. Canberra uses the Mercator projection, which distorts the size of regions near the poles.