Democratic Republic of the Congo is clearly the larger of the two: about 2,334,703 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.
Democratic Republic of the Congo 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 map muddied it further: Mercator inflates Democratic Republic of the Congo about 1× and Iran about 1.4×, so on a Mercator-style map this pair appears 1× apart instead of the true 1.4×.
Iran fits 1× into Democratic Republic of the Congo.