Fun facts
The standard size of a 5-room HDB flat is 110 square meters (sq m).
Sources:
https://assets.hdb.gov.sg/residential/buying-a-flat/finding-a-flat/my-nice-home-gallery/eamnh/5room.html
https://assets.hdb.gov.sg/residential/buying-a-flat/finding-a-flat/my-nice-home-gallery/eamnh19/5room.html
https://assets.hdb.gov.sg/residential/buying-a-flat/finding-a-flat/my-nice-home-gallery/eamnh20/5room.html
https://assets.hdb.gov.sg/residential/buying-a-flat/finding-a-flat/my-nice-home-gallery/eamnh22/5room.html
https://assets.hdb.gov.sg/residential/buying-a-flat/finding-a-flat/my-nice-home-gallery/eamnh23/5room.html
1 square foot (sq ft) is equal to exactly 0.092 903 04 sq m.
100 sq m is greater than ROUNDDOWN(100 / 0.09290304, 0) = 1,076 sq ft
120 sq m is greater than ROUNDUP(120 / 0.09290304, 0) = 1,292 sq ft
Therefore we can clearly say that a 5-room HDB flat is between 1,076 and 1,292 sq ft.