What is the concept of a 20-square-meter house? About how big?

It is 5 meters long and 4 meters wide.

A single room of 20 square meters is relatively small. Generally, the area of a bedroom is about 20 square meters. You can directly imagine it as a rectangle, 5 meters long and 4 meters wide. Normal small bedroom can't put too much furniture, otherwise it will be particularly crowded, depressed to live, and the whole looks messy.

20 square meters, depending on whether you have property area or usable area. Excluding the shared property area, it may only be 15 square meters. This area can only put down the bed and wardrobe, or add a mini toilet. If the use area is 20 square meters, you can get a bed of 1.5 meters and a wardrobe of 1.2 meters to leave room for the door.