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Gross floor area, saleable floor area, and efficiency explained

Hong Kong use an unique system where Gross floor area include a sharepart of common spaces, thus two blocks with different number of identical apartment per floor could had different gross floor area, because in one block the common areas would be divided to fewer apartments than in other block. In other countries Gross floor area meaning is like Hong Kong’s Saleable area.

Net floor area is the internal room space between face of walls.

Saleable floor area include full thickness of external walls, half thickness of walls shared with other units, internal walls thickness, as well as balconies, but exclude bay windows.

Gross floor area also include a sharepart of common areas (lifts, staircases, corridors) so it should not been taken in serious.

Housing Authority (public housing) shows internal floor area in case of PRH estates, while for TPS, HOS and PSPS estates it shows saleable and gross floor area.

Most private developers, as well as all property classifieds websites, published gross floor area as primary value of apartment size, confusing people. Only in 2012 or 2013, websites like and added saleable floor area beside gross floor area in every listing.

The efficiency (Saleable floor area) is usually 75-85% of Gross floor area, higher value for the blocks with bigger apartments and for low-rise blocks, since the common area of a blocks with a given number of units per floor is approximately same for regardless of apartments size. More details about what is gross floor area and efficiency here and

As home owner, you may be interested in internal floor area, but the percentage of internal floor area from saleable area vary much, as newer and taller buildings require thicker walls, take a look at 64-storey The Masterpiece, at lower floors structural walls are 100 – 120 cm thick, higher floors have thinner walls so larger rooms.



  1. Just an update for this session.

    Under the Residential Properties (First-hand Sales) Ordinance, saleable area will be the only basis that vendors can use to quote property size and property price per square foot/per square meter in the sales brochures, price lists and advertisements of first-hand residential properties.


    It is also now the market practice that the Saleable Floor Area is more popular than GFA.

  2. I have a question and wonder if you can help me?

    APP 151 if a building includes certain green facilities, they will not be included in the GFA calculation. Aim I right to think technically this will mean a greater amount of GFA that can be sellable area? If the developer, for whatever reason can not increase the sellable area, he/she wont make more money. Also, the developer still need to pay money to build these green facilities.

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