Amsterdam is about 10 times smaller than Johannesburg.

Johannesburg is approximately 1,644 sq km, while Amsterdam is approximately 166 sq km, making Amsterdam 10.08% the size of Johannesburg.
Tip: This to-scale comparison of Johannesburg vs. Amsterdam 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.