Manhattan is about 2.3 times smaller than Boston.

Boston is approximately 124 sq km, while Manhattan is approximately 55 km² (21 sq mi), making Manhattan 43.98% the size of Boston.
Tip: This to-scale comparison of Boston vs. Manhattan 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.