Ulm is about 1.4 times smaller than Amsterdam.

Amsterdam is approximately 166 sq km, while Ulm (map shows its 55 named neighbourhoods; the area covers the whole city) is approximately 119 sq km, making Ulm 71.6% the size of Amsterdam.
Tip: This to-scale comparison of Amsterdam vs. Ulm uses the Mercator projection, which distorts the size of regions near the poles.
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