Mauritania covers 1,038,352 km² km² on the new Equal Earth world map — 0.8%% of all land on Earth, making it the 29th largest country in the world and the 11th largest in Africa. At 20° latitude Mercator only inflates Mauritania by about 14%%, so the old and new maps largely agree on it — unlike the far north, where Mercator's stretch is dramatic.
For scale: Mauritania is roughly the same size as Egypt (1,003,707 km² km²).
You could fit 3 of Finland inside Mauritania.