Birmingham is about 4.1 times smaller than London.

London (including the 32 boroughs of greater London) is approximately 1,572 sq km, while Birmingham (map shows its 87 named neighbourhoods; the area covers the whole city) is approximately 381 sq km, making Birmingham 24.23% the size of London.
Tip: This to-scale comparison of London vs. Birmingham 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.