Closer than most people guess: Libya (1,626,369 km² km²) is only about 18%% larger than Saudi Arabia (1,925,871 km² km²).
Libya sits in Africa, Saudi Arabia 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 1.2×.
The old Mercator map treated both about equally (1.3× vs 1.2× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Libya fits 1× into Saudi Arabia.