When you first look at a Hong Kong property brochure or price list, you see two numbers for area: gross floor area (GFA) and saleable area (SA). Many buyers, especially first timers, assume these are interchangeable or that the difference is small. In reality, the gap can be 20% to 30% or more. Understanding gross vs saleable area is essential to comparing flats, calculating real price per square foot, and avoiding overpaying.

This article explains the definitions, legal background, typical differences, and practical tips for using these figures when you evaluate a property. We also link to other resources on buying property in Hong Kong and deciphering price lists.

What Is Gross Floor Area (GFA)?

Gross floor area is the total floor area within the outer walls of a building, including all common areas and structural elements. In Hong Kong, the definition is set by the Buildings Department and the Land Department. GFA includes:

  • All internal floor space of a flat, measured from the centre of external walls.
  • Common areas such as lobbies, staircases, lift shafts, corridors, and clubhouse facilities.
  • Structural elements like columns, beams, and walls.
  • Balconies, utility platforms, and air-conditioning plant platforms (though these may be counted partly or fully depending on the building plan approval).

For a residential development, the GFA is often the sum of all flats plus the shared amenities. Developers use GFA to calculate the total buildable area allowed on a site under the lease conditions. When you see a price list that quotes a price per square foot based on GFA, that price is lower than the price per square foot based on saleable area, because GFA includes non-usable space.

How GFA Is Calculated

The Hong Kong Buildings Department's Code of Practice for Building (Plan Approval) specifies that GFA is measured to the external face of the external walls. For a typical 700-square-foot flat, the GFA might be around 900 square feet if you include the share of common areas and structural thickness. The exact ratio varies by building design and the number of flats per floor.

In older buildings (pre-1980s), GFA was often close to saleable area because common areas were smaller and walls were thinner. In modern luxury towers, the difference can be substantial. For example, a 1,200-square-foot GFA flat in a new development in Kowloon may have a saleable area of only 850 to 900 square feet.

What Is Saleable Area (SA)?

Saleable area is the floor area that a buyer can actually use inside the flat. It excludes common areas, external walls, and structural elements. The Hong Kong government introduced mandatory disclosure of saleable area in 2013 under the Residential Properties (First-hand Sales) Ordinance. Since then, all first-hand sales brochures and price lists must show the saleable area in square feet or square metres.

Saleable area includes:

  • The area inside the flat measured from the internal face of external walls.
  • Internal partitions and columns within the flat.
  • Balconies, utility platforms, and air-conditioning platforms (if they are part of the flat's exclusive use).

It does not include:

  • Common areas (lobbies, corridors, staircases, lifts).
  • External walls (the thickness is excluded).
  • Share of clubhouse or management facilities.

Why Saleable Area Matters

Saleable area is the true usable space. When you compare two flats, you should always compare price per square foot based on saleable area. A flat with a low GFA price but a high GFA-to-SA ratio may actually be more expensive per usable square foot than a flat with a higher GFA price but a lower ratio.

For example, consider two flats in the same district:

  • Flat A: GFA 800 sq ft, SA 600 sq ft, price HK$8 million. Price per GFA sq ft = HK$10,000. Price per SA sq ft = HK$13,333.
  • Flat B: GFA 750 sq ft, SA 650 sq ft, price HK$8.2 million. Price per GFA sq ft = HK$10,933. Price per SA sq ft = HK$12,615.

Flat B has a higher GFA price but a lower SA price. The buyer gets more usable space for each dollar spent. If you only look at GFA, you might mistakenly think Flat A is cheaper.

Typical Differences Between Gross and Saleable Area

The difference between GFA and SA is expressed as a ratio or percentage. In Hong Kong, the ratio is commonly called the "efficiency ratio" or "saleable ratio." It is calculated as SA divided by GFA. For example, if SA is 700 sq ft and GFA is 900 sq ft, the efficiency ratio is 77.8%.

Typical ranges for different property types in Hong Kong:

  • Old tenement buildings (1950s-1970s): Efficiency ratio 85% to 95%. Walls are thinner, common areas minimal. A 500 sq ft GFA flat may have 450 sq ft SA.
  • 1980s-1990s private housing estates: Efficiency ratio 80% to 88%. Larger common areas but still relatively efficient. Example: Taikoo Shing (built 1977-1987) has ratios around 82-86%.
  • 2000s-2010s luxury developments: Efficiency ratio 70% to 80%. Thicker walls, larger lobbies, more amenities. Example: The Harbourside (Kowloon Station) has ratios around 72-78%.
  • Post-2013 new developments (especially small flats): Efficiency ratio 60% to 75%. Developers maximise GFA by including large balconies, utility platforms, and air-conditioning platforms that are counted in GFA but not in SA. Some micro-flats in areas like Mong Kok or Tsuen Wan have ratios below 60%.

According to data from the Rating and Valuation Department, the average efficiency ratio for new private residential flats completed in 2022 was 72.5%. That means for every 1,000 sq ft of GFA, only 725 sq ft is usable inside the flat.

How to Read a Sales Brochure

Under the Residential Properties (First-hand Sales) Ordinance, developers must provide a sales brochure that clearly states both GFA and SA for each flat. The brochure must also show a floor plan with dimensions. You can find the SA listed in a table alongside the GFA. Look for the column labelled "Saleable Area" or "Internal Floor Area." Some older brochures (before 2013) may only show GFA.

For more details on interpreting brochures, see our article Reading a Sales Brochure.

Key Items to Check

  • Balconies and utility platforms: These are included in GFA but may be listed separately in SA as "balcony" or "utility platform." The SA figure for the flat usually includes these areas, but they are not internal floor space. A flat with a large balcony may have a high SA but less actual indoor room.
  • Air-conditioning platforms: In many new developments, these are counted in GFA but excluded from SA. They are small ledges outside the window, not usable as floor area.
  • Bay windows: Bay windows are often counted in GFA but not in SA. They add to the gross area but do not increase usable floor space.
  • Structural columns: Columns inside the flat are included in SA because they are within the internal walls. However, they reduce usable space. A flat with many columns may have a higher SA but less practical area.

When you visit a show flat, ask for the saleable area and the dimensions of each room. Developers sometimes design show flats with smaller furniture or no partitions to make the space look larger. Compare the floor plan with the actual dimensions.

Impact on Mortgage Valuation

Banks in Hong Kong value properties based on the market price per square foot of saleable area. They use SA rather than GFA because SA reflects the usable space that a buyer can enjoy. When you apply for a mortgage, the bank will send a surveyor to measure the flat. The surveyor will calculate the SA and compare it with recent transactions for similar flats in the same building or estate.

If the efficiency ratio of a flat is unusually low (below 65% for a new development), the bank may apply a discount to the valuation. For example, a 400 sq ft GFA micro-flat with only 250 sq ft SA may be valued at a lower price per sq ft than a traditional flat of the same SA. This can affect the loan-to-value ratio and the amount you can borrow.

For more on financing, see The Complete Guide to Buying Property in Hong Kong.

Price per Square Foot: GFA vs SA

Most price lists published by developers show both the total price and the price per square foot based on GFA. However, the price per square foot based on SA is not always displayed. You can calculate it yourself: divide the total price by the SA.

Example from a real project: In 2023, the new development One Central Place in Tseung Kwan O had a flat with GFA 520 sq ft, SA 380 sq ft, and a price of HK$7.8 million. The price per GFA sq ft was HK$15,000. The price per SA sq ft was HK$20,526. The efficiency ratio was 73%. A buyer who only looked at the GFA price might think the flat was cheaper than a nearby older flat with an 85% ratio. But per usable square foot, the older flat might have been a better deal.

When you compare properties across different developments, always use SA price per square foot. This is the standard practice among experienced investors and real estate agents. For second-hand properties, agents usually quote the price based on SA because the data from the Land Registry records the saleable area (since 2013). For older properties, the Land Registry may only record GFA, so you may need to ask the agent for the SA.

Legal and Regulatory Background

The Residential Properties (First-hand Sales) Ordinance (Cap. 621) came into effect on 29 April 2013. It requires developers to provide accurate information about saleable area in all sales materials. The ordinance defines saleable area as:

"the floor area of a residential property, measured from the interior of the external walls, and includes the area of any balcony, utility platform, and air-conditioning platform that forms part of the property."

The ordinance also requires that the saleable area be expressed in square metres and square feet. Any discrepancy between the advertised area and the actual area can lead to penalties. The Estate Agents Authority (EAA) also requires estate agents to disclose both GFA and SA when marketing a property.

For second-hand properties, the Land Registry records the area as stated in the assignment. Before 2013, many assignments only recorded GFA. If you are buying a second-hand flat built before 2013, you should check the floor plan and, if possible, measure the flat yourself or hire a surveyor. The agent should provide the SA based on the building plan or a previous survey.

For more on the legal aspects, see Understanding Leasehold and Freehold and How the Hong Kong Property Market Works.

Common Misconceptions

"Gross area includes everything, so it's the total area I own."

No. You do not own the common areas. You own a share of them as part of the building's common parts, but you cannot use them exclusively. The GFA includes your share of common areas, but that space is not part of your flat.

"A higher GFA always means a bigger flat."

Not necessarily. Two flats with the same GFA can have very different SA depending on the building design. A flat with a large balcony and thick external walls may have a smaller internal space than a flat with a simple rectangular shape and thin walls.

"Saleable area is the same as carpet area."

In Hong Kong, saleable area is sometimes called "carpet area" in colloquial usage, but technically they differ. Carpet area usually excludes all walls and columns. Saleable area includes internal walls and columns. The actual floor area you can cover with a carpet is smaller than the saleable area. Some developers use "carpet area" in marketing, but the official term in the ordinance is saleable area.

"New developments are more efficient."

On the contrary, new developments often have lower efficiency ratios because of thicker walls, larger common areas, and more balconies. A 30-year-old flat in a public housing estate may have an efficiency ratio above 90%, while a new luxury flat may have only 70%. However, older flats may have less modern layouts and smaller windows.

Practical Tips for Buyers

  1. Always ask for the saleable area. If the agent or developer does not provide it, request it in writing. For second-hand properties, check the Land Registry record or ask the owner for the assignment.
  2. Calculate the efficiency ratio. Divide SA by GFA. If the ratio is below 70%, consider whether the extra common area is worth the cost. For a family that needs maximum indoor space, a higher ratio is better.
  3. Compare price per SA square foot. Use this figure to compare flats in different buildings, districts, or age groups. Ignore the GFA price per square foot.
  4. Visit the flat and measure. Bring a laser measurer and check the dimensions of each room. Compare with the brochure. If the flat is under construction, ask for the as-built floor plan.
  5. Check the balcony and utility platform. These areas are included in SA but are not indoor space. A flat with a large balcony may have a high SA but a small living room.
  6. Consider the impact on mortgage. If the efficiency ratio is very low, the bank may value the property lower. Get a pre-approval or ask the bank's surveyor for an estimated value.
  7. Read the price list carefully. Some price lists show discounts or rebates that affect the net price. The price per square foot may be based on the discounted price. See our article Deciphering Price Lists for more.

Case Study: Comparing Two Flats

Let's use a concrete example from a recent development in Tuen Mun. Flat X: GFA 600 sq ft, SA 430 sq ft, price HK$6.5 million. Price per GFA sq ft = HK$10,833. Price per SA sq ft = HK$15,116. Efficiency ratio = 71.7%.

Flat Y: GFA 550 sq ft, SA 440 sq ft, price HK$6.6 million. Price per GFA sq ft = HK$12,000. Price per SA sq ft = HK$15,000. Efficiency ratio = 80%.

Flat Y has a higher GFA price per square foot but a slightly lower SA price per square foot. Flat Y also has 10 more square feet of usable space. For the same budget, Flat Y is the better choice if you value indoor space. However, Flat X may have a larger balcony or a better view. You need to weigh the trade-offs.

For more on comparing new and second-hand properties, see New Developments vs Second-Hand.

Market Trends and Future Changes

In recent years, the Hong Kong government has considered reforming the way floor area is disclosed. In 2022, the Transport and Housing Bureau proposed that all property advertisements should prominently display the saleable area and the price per saleable area. Some developers have already started doing this voluntarily. However, as of 2025, the law still requires both GFA and SA to be shown.

The trend towards smaller flats (so-called nano flats) has pushed efficiency ratios lower. In 2023, the average SA of a new flat in Hong Kong was 430 sq ft, down from 480 sq ft in 2015, according to the Rating and Valuation Department. Developers are designing flats with more balconies and utility platforms to increase GFA while keeping SA small. Buyers should be vigilant.

For a broader view of market cycles, see Market Trends and Cycles.

Understanding gross vs saleable area is not just a technical detail. It directly affects the price you pay, the space you get, and the value of your investment. Always use saleable area as your primary reference. Ask questions, check documents, and never rely on GFA alone. With the right knowledge, you can make a more informed decision and avoid costly mistakes.

Related Articles

  • The Complete Guide to Buying Property in Hong Kong
  • How the Hong Kong Property Market Works
  • New Developments vs Second-Hand
  • Understanding Leasehold and Freehold
  • Market Trends and Cycles
  • Reading a Sales Brochure
  • Deciphering Price Lists