Btu Calculation

For most new HDB flats.
4 rooms.
Estimated btu for the bedrooms are 9k btu each.
Living will be 18k btu.

3 rooms
Estimated btu for the bedrooms are 9k btu each.
Living will be 12k/18k.

If you hack the master room and bedroom 2 into one room, i will suggest at least a 12k btu. but 18k will be more comfortable in terms of cooling.

Rough guide for calculation of btu.
Take your square area of the room multiply by a factor of 400-500.
400 for lower requirements/number of people in the area.
500 for higher requirements/number of people in the area.

Say a bedroom square area is 18 square metre.
18 x 450 (middle range) = 8100.
8100 nearest btu is 9k btu.

This formula is taking into account of a ceiling height of 2.5-3 metres.

The same formula can be used for pte apartments.
But for calculation of the living/dining area if the ceiling is of a higher height.
Maybe u can multiply by 600 instead of 500 to factor in the higher ceiling.

A ceiling fan may be useful too for faster distribution of the cold air.