Algeria dwarfs China: about 2,322,788 km² km² against 9,371,225 km² km². At true size Algeria is about 4× larger — the whole of China fits into Algeria roughly 4 times.
Algeria sits in Africa, China 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 4×.
The old Mercator map treated both about equally (1.3× vs 1.6× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Algeria fits 4× into China.