Efficiency ratio: how much of the flat you actually get
Efficiency ratio (實用率) tells you what share of the price you pay corresponds to space you can actually use. It is a market term, not a legal one, calculated as saleable area divided by gross floor area. Because gross floor area is no longer published in first-hand sales material—Hong Kong’s Residential Properties (First-hand Sales) Ordinance (Cap. 621) stopped that—you will rarely see the ratio stated officially. But when you have both figures from the land registry or an older transaction, the ratio explains how a flat’s size compares to the building’s total footprint.
What the ratio measures
Efficiency ratio = saleable area ÷ gross area × 100%.
Saleable area, as defined by the Sales of First-hand Residential Properties Authority (SRPA), is the floor area measured from the exterior of the enclosing walls. It includes balconies, utility platforms and verandahs, but excludes ten specific items: air-conditioning plant room, bay window, cockloft, flat roof, garden, parking space, roof, stairhood, terrace and yard. These excluded items must be listed separately in the sales brochure and price list.
Gross area is a broader figure that adds to the saleable area the thickness of all external walls, common areas (lobbies, corridors, staircases, lift shafts), clubhouse facilities, car park apportionment and sometimes even the building’s structural core. Because gross area was once the headline figure used in marketing, the efficiency ratio was the tool buyers used to compare how much of that headline was actually theirs.
Today, first-hand vendors are prohibited from showing any gross floor area figure in their area schedules. They may only list the saleable area and, separately, the ten excluded items. This means you cannot compute a precise efficiency ratio from a new development’s brochure. You can, however, reconstruct it if you find the gross floor area from the building’s occupation permit or from older sale records.
Typical ranges for different building types
The efficiency ratio varies enormously by building era and design. Here is a broad breakdown based on common market observations—no official figures exist, so treat these as guidelines you should verify against the specific property.
| Building type / era | Approximate efficiency ratio range | Key drivers |
|---|---|---|
| Pre-1970s walk-up (no lift, no clubhouse) | 85% to 90% | Thin walls, minimal common corridors, no lift lobby, no car park. Nearly all gross area is your flat. |
| 1970s–1990s estate (with lifts, basic facilities) | 80% to 85% | Lift shaft, lobby, staircase. Clubhouse small or absent. Car park often a separate structure. |
| 2000s modern estate (clubhouse-heavy) | 70% to 78% | Large clubhouse, multiple lifts, grand lobbies, swimming pool, gym, car park apportioned to gross area. |
| Recent luxury development (facade features, bay windows) | 60% to 72% | Bay windows, thick external walls, large balconies, deep utility platforms, extensive clubhouse. Also: air-con plant rooms that are excluded from saleable but part of gross. |
| Small-scale redevelopment (single tower, limited facilities) | 75% to 82% | Few common areas, typically one lift, no clubhouse. Efficiency higher than a mega-estate but lower than a walk-up. |
What drives the ratio down
A low efficiency ratio means a bigger share of the building’s total area is consumed by things that are not your flat. The main contributors:
- Clubhouse provision. Swimming pools, function rooms, gyms and landscaped gardens are counted in gross area. The more facilities, the more space is carved out of each flat’s share.
- Lift lobbies and corridors. A building with two or three lifts per floor, a wide corridor and a grand entrance lobby eats up floor area that could otherwise be part of flats.
- Car park apportionment. In many developments, the car park’s floor area is distributed across the flats’ gross area, lowering the ratio.
- Structural features. Thick external walls, large bay windows and air-conditioning plant rooms add to gross area without adding to saleable area. Bay windows and plant rooms are excluded from saleable area under the ordinance.
- Balconies and utility platforms. While these are included in saleable area, they are often long and narrow—usable space, but less flexible than an equivalent area of interior floor.
Why a high ratio is not automatically better
An 88% efficiency ratio sounds excellent, but it often reflects a building with few or no shared amenities. A 1970s walk-up may give you that figure, yet you would have no lift, no clubhouse, no car park and possibly no management office. You would need to climb stairs, carry groceries and suffer the absence of facilities that modern buyers expect.
A modern development with a 72% ratio may compensate with a well-equipped clubhouse, a children’s play area, a 24-hour concierge and a car park. The 16 percentage-point drop in efficiency is the price you pay for those shared spaces. For some buyers—especially families with children—the facilities are worth more than a few extra square feet of interior space.
Also, a very high ratio in an older building may be misleading because the gross area was measured differently decades ago. Some pre-1990 buildings used an older measurement standard that excluded certain common areas from gross. Always check how gross was defined at the time.
The ‘發水’ (water padding) criticism and the regulatory response
Until the early 2010s, developers routinely inflated gross floor areas by including structural features that added little usable space—large bay windows, oversized plant rooms, decorative cladding. These features were called ‘發水’ (literally “water padding”) because they made the gross number look bigger while the saleable area stayed modest. A flat could show a 75% efficiency ratio but, if you deducted the bay window and plant room, the actual livable space was far smaller.
The Residential Properties (First-hand Sales) Ordinance (Cap. 621), which came into full effect on 29 April 2013, directly tackled this. The SRPA’s rules now require that sales brochures and price lists for first-hand properties show only the saleable area and the ten excluded items—no gross floor area at all. Section 23(1) and Section 31(9) prohibit vendors from adding any other area figure. This ended the practice of marketing a flat by its gross area. While the ordinance did not abolish the efficiency ratio, it removed the figure that was historically used to inflate it.
The effect: you no longer see “efficiency ratio” advertised for new flats. The buyer must focus solely on the saleable area. The ratio is still a useful concept when comparing older buildings or when you obtain gross area from the land registry, but it is no longer a marketing weapon.
How to compute the ratio yourself
If you have both figures—for example, from a land registry record for a second-hand flat or from an old brochure—simply divide saleable area by gross area. For a hypothetical flat of 500 square feet saleable and 650 square feet gross, the efficiency ratio is 500 ÷ 650 = 76.9%.
But for first-hand flats, you will not find gross area in the official materials. The SRPA FAQ confirms that only saleable area and the ten Schedule 2 items are permitted. To get a sense of efficiency in a new development, you must ask the developer directly or check the occupation permit once the building is completed. Even then, gross floor area on the permit may include car parks and clubhouses that are not distributed equally to each flat.
What to check next
- For a second-hand flat: Ask the agent for the saleable area (which must be stated in the listing) and, if possible, the gross area from the land search. Compute the ratio, then compare with other flats in the same building or estate. A large gap between two similar flats may indicate an older measurement standard.
- For a first-hand flat: Ignore the efficiency ratio entirely. Use the saleable area as your only size reference. If you want to understand the building’s common-area footprint, visit the show flat and ask for the floor plan of the typical floor and the clubhouse. You cannot compute a precise ratio, but you can see how much corridor and lobby space exists.
- Compare like with like: Do not compare a 1970s walk-up’s efficiency ratio with a 2020s clubhouse estate’s ratio. They are different products. Decide which trade-off—space versus amenities—matters more to you.
- Verify with the SRPA: The Sales of First-hand Residential Properties Authority’s website (srpa.gov.hk) has the full definition of saleable area under Cap. 621. If you suspect a developer is misrepresenting area, you can file a complaint.