Boise is about 1.6 times smaller than Portland.

Portland is approximately 346 sq km, while Boise is approximately 221 sq km, making Boise 63.79% the size of Portland.
Tip: This to-scale comparison of Portland vs. Boise uses the Mercator projection, which distorts the size of regions near the poles.
Our free app, MapSize by MyLifeElsewhere — compare any two places, to scale on your mobile device.