Arlington is about 1.8 times smaller than San Francisco.

San Francisco (including the city proper only) is approximately 121 sq km, while Arlington (map shows its 62 named neighbourhoods; the area covers the whole city) is approximately 67 sq km, making Arlington 55.65% the size of San Francisco.
Tip: This to-scale comparison of San Francisco vs. Arlington 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.