Montserrat is about 1.7 times bigger than British Indian Ocean Territory.

British Indian Ocean Territory is approximately 60 sq km, while Montserrat is approximately 102 sq km, making Montserrat 70% larger than British Indian Ocean Territory.
Tip: This to-scale comparison of British Indian Ocean Territory vs. Montserrat uses the Mercator projection, which distorts the size of regions near the poles.
Compare further: Montserrat vs. British Indian Ocean Territory