District of Columbia is about 3 times bigger than British Indian Ocean Territory.

British Indian Ocean Territory is approximately 60 sq km, while District of Columbia is approximately 177 sq km, making District of Columbia 195% larger than British Indian Ocean Territory.
Tip: This to-scale comparison of British Indian Ocean Territory vs. District of Columbia uses the Mercator projection, which distorts the size of regions near the poles.

Compare further: District of Columbia vs. British Indian Ocean Territory