Algeria is clearly the larger of the two: about 2,322,788 km² km² against 1,622,847 km² km², roughly 1.4× at true size. Drag one onto the other on the map above to feel the gap.
Algeria sits in Africa, Iran in Asia. On the old Mercator map the latitude gap distorted how large each felt beside the other; at true size the answer is simply 1.4×.
The old Mercator map treated both about equally (1.3× vs 1.4× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Iran fits 1× into Algeria.