Short answer: The gross-to-net area gap is calculated by subtracting the verified net area from a gross area measured under a stated definition: area gap = gross area - net area. The gap as a share of gross is (gross - net) / gross × 100, while net-use efficiency is net / gross × 100. The arithmetic is easy; selecting the correct gross figure is the difficult part. In Türkiye, a unit’s own gross area, its total gross area after private annexes, and its general gross area after allocated common areas are different concepts. An advertisement saying “140 m² gross, 98 m² net” is incomplete unless it explains what the 140 m² includes.
The purpose is not to find the largest advertised number but to find a comparable number. Two apartments in the same building can have different efficiency because of geometry, structural columns, wall thickness, service shafts, balconies, annexes and common-area allocation. When reviewing current property listings, ask every seller the same question: “Is this net area, unit gross area, total gross area or general gross area?” That single discipline prevents many false comparisons.
Why are gross and net square metres so often confused?
In everyday property marketing, “gross” may refer to the external outline of the apartment, the apartment including its walls and balcony, the apartment plus a storage annex, or an enlarged figure that also allocates stairs, lift halls and other shared areas. When one word is used for several calculation bases, a larger marketing number does not necessarily mean more space inside the home. A 112.5 m² unit-gross apartment and a 140 m² general-gross apartment may both provide exactly 98 m² of verified net area.
A second source of confusion is treating an on-site measurement and an official project calculation as interchangeable. Measuring clear room dimensions with a laser helps a buyer understand usable space. Official area categories, however, depend on what the current rules and the approved architectural project include or exclude. A tape measure can show the living room width, but it cannot prove how common areas were apportioned or whether a basement room is a legally registered annex to the unit.
A third error is relying on a universal conversion such as “net is always 80% of gross.” No such constant exists. Façade length, unit shape, structural system, internal wall density, service cores, the number of lifts, floor corridors, shared facilities and the allocation method all change the ratio. Eighty per cent can be the result of one example; it is not a substitute for project documents.
The area categories that must be separated in Türkiye
The Planned Areas Zoning Regulation distinguishes several concepts rather than defining one universal gross area. Buyers should separate net unit area, unit gross area, annex gross area, total unit gross area and general unit gross area. Before doing any calculation, ask the seller or project company to name the category in writing. The following table translates those concepts into a practical buyer framework; the current regulation, the approved project and the competent authority’s records remain decisive for a specific property.
| Area category | Basic scope | What must not be confused | Buyer use |
|---|---|---|---|
| Net unit area | Clear area between walls under the defined inclusions and exclusions, including eligible internally connected rooms | Columns, shafts, shared areas, open balconies, terraces and separate annexes are not automatically net area | Understanding usable enclosed space and room planning |
| Unit gross area | Area enclosed by the unit’s external contours, subject to defined treatment of voids, walls and boundaries | Allocated common areas and separately accessed annexes are different categories | Comparing the physical envelope of the apartment itself |
| Annex gross area | Area of a separately accessed space outside the unit that belongs only to that unit, such as a documented store | A room used in practice is not automatically a lawful registered annex | Valuing private storage or similar rights separately |
| Total unit gross area | Unit gross area plus the gross area of its private annex or annexes | This is not yet the general gross figure with common-area allocation | Combining the apartment and its private annexes |
| General unit gross area | Total unit gross area plus the share allocated from common areas | It does not represent floor space that can be walked inside the apartment | Understanding the complete project allocation behind a marketed total |
What is included in net area?
Net area is more precise than a rough total of room labels. Under the regulatory approach, it is the clean area inside the independent unit between walls after applying specified exclusions. Eligible spaces on internally connected levels, including relevant parts of duplex or roof-level arrangements, may be assessed together. Structural columns, service and ventilation shafts, light wells, gallery and lift voids, plant rooms and certain low spaces beneath stairs are excluded.
Open projections, balconies, ground, floor and roof terraces, floor or roof gardens and similar spaces with at least one open side are not treated as net unit area. A separately accessed storage annex and shared areas are also not part of the unit’s net area. This does not make a balcony worthless. It means the balcony should be disclosed on its own line instead of being presented as enclosed net living area.
During a practical survey, clear dimensions are taken between finished wall surfaces. Door thresholds, recesses, fixed joinery, sloping ceilings and balconies enclosed after construction need careful classification. Physical use does not by itself establish lawful area. Record any difference between the existing layout and the approved plan instead of silently adding it to the net figure.
How should unit gross area be read?
Unit gross area is not calculated by adding an arbitrary percentage to net area. It is based on the contours of the independent unit, with specific exclusions for shafts, light wells, ventilation ducts and gallery voids. At boundaries with another unit or a common area, a wall centreline may be relevant under the applicable definition. Internal walls, columns and structural components make gross area larger than clear net area.
If a unit consists of several internally connected levels, the relevant spaces belonging to the unit are considered together. A basement store with a separate entrance is not simply treated as an internal room; it must be identified as an annex and disclosed separately. For this reason, a dimensioned approved floor plan is more valuable than a coloured sales brochure when checking the gross figure.
Formulas for the gross-net gap and efficiency
Once the area definitions are fixed, the calculation is straightforward. Always write the gross category next to the result. “The gap is 30%” is ambiguous; “the net gap against general gross area is 30%” is auditable.
- Area gap: selected gross area - verified net area.
- Gap as a share of gross: (gross area - net area) / gross area × 100.
- Net-use efficiency: net area / gross area × 100.
- Gross-to-net multiplier: gross area / net area.
- Price per net square metre: total purchase price / verified net area.
- Price per unit-gross square metre: total purchase price / unit gross area.
When 98 m² net is compared with 112.5 m² unit gross, efficiency is approximately 87.1% and the gap is approximately 12.9% of gross. If the denominator is changed to 140 m² general gross, the same apartment produces 70% net efficiency. Nothing happened to the home; only the calculation base changed.
A complete worked example
Assume the eligible clear room areas total 98 m². Internal walls, columns and other elements within the apartment’s gross envelope add 14.5 m², producing 112.5 m² unit gross area. A documented separate store contributes 4.5 m² gross, taking total unit gross area to 117 m². A further 23 m² common-area share takes general unit gross area to 140 m².
| Calculation item | Area | Running total | Interpretation |
|---|---|---|---|
| Living room | 27.4 m² | 27.4 m² | Clear room area |
| Kitchen | 12.1 m² | 39.5 m² | Clear usable area |
| Three bedrooms | 37.3 m² | 76.8 m² | 14.6 + 11.9 + 10.8 m² |
| Bathroom and WC | 5.6 m² | 82.4 m² | Eligible clear area |
| Entrance and corridors | 12.2 m² | 94.6 m² | Internal circulation |
| Storage and dressing | 3.4 m² | 98.0 m² net | Verified net unit area |
| Walls, columns and gross-envelope difference | 14.5 m² | 112.5 m² | Unit gross area |
| Separate storage annex | 4.5 m² | 117.0 m² | Total unit gross area |
| Allocated common-area share | 23.0 m² | 140.0 m² | General unit gross area |
Two different gap statements are mathematically correct in this example. Against unit gross area, the gap is 112.5 - 98 = 14.5 m². Against general gross area, it is 140 - 98 = 42 m². The first explains conversion within the apartment envelope; the second shows the marketed total after annexes and common-area allocation. A seller must identify which statement is being used.
If the asking price were TRY 9,800,000, the apparent unit price would be TRY 70,000/m² against general gross, about TRY 87,111/m² against unit gross and TRY 100,000/m² against net area. Dividing by the largest denominator can make a property look artificially inexpensive. Calculate price per verified net square metre and price per unit-gross square metre separately.
How to measure net area on site
An on-site survey does not amend the approved project, but it tests whether the existing home and marketing information are plausible. Prepare a laser meter, a paper or digital sketch, photographs and a calculation sheet. Decide how you will split irregular shapes, record recesses and treat sloping ceilings before starting.
- Divide each room into rectangles or triangles instead of forcing an irregular plan into one length-by-width calculation.
- Measure clear dimensions from finished wall surface to finished wall surface and mark every measurement point.
- Use length × width for rectangles and base × perpendicular height / 2 for triangles.
- Measure columns, shafts, unusable recesses and voids separately and deduct them from the appropriate item.
- Include eligible entrance, corridor, bathroom, WC, internal store and internally connected spaces.
- Keep balconies, terraces, separate stores, parking and shared areas outside enclosed net area and report them separately.
- Sum the rooms, then compare the result with the approved architectural plan and area schedule.
Averaging two opposing walls in an irregular room gives only a quick estimate. Older buildings with non-square walls may require diagonals or a professional survey. Skirting, finishes and furniture can affect readings. Do not publish excessive decimal precision when the measurement conditions do not support it.
Why can you not calculate full gross area from inside the home?
Most clear room dimensions can be surveyed from the interior; a defensible gross figure needs project information about wall centrelines, external contours, voids, annex boundaries and common-area allocation. Standing in the living room cannot reveal whether the whole party wall or its centreline is used, which schedule allocated the lift hall, or whether a basement room legally belongs to the apartment.
Unauthorised changes create another problem. A balcony may have been enclosed, an internal wall moved or a shared corridor absorbed into the unit. The space may appear usable, but its physical condition does not prove compliance with the approved project. Do not conclude that the deed or municipality is wrong simply because a laser total differs. First align the date, definition and revision of every document; then obtain architectural, valuation or legal assistance where necessary.
Which documents should be checked together?
A listing page or a photograph of a title document is not enough to verify area. Especially for off-plan purchases, the relevant floor plan, area schedule and contract terminology must agree. Turkish Ministry guidance on square-metre representations has also emphasised identifying the independent unit, its annexes and its common-area components separately.
- Approved architectural project attached to the permit: shows the unit boundary, room layout, balconies, shafts and annexes.
- Area schedule or project calculations: should explain how net, unit gross, annex and common-area figures are formed.
- Sale or preliminary sale contract: must state a square-metre figure together with its area category.
- Condominium, construction-servitude and annex records: help verify whether a store or similar space is legally tied to the unit.
- Occupancy permit and municipal file: support review of the completed building’s approval history.
- Site measurements and photographs: document whether the existing condition matches the project.
Compare revision dates. An early brochure may reflect an old plan, the contract a revised plan and the finished apartment an unauthorised alteration. Several drawings can carry the same unit type name but different revision numbers. The area dispute cannot be resolved until the latest approved document is identified.
How should the common-area share be questioned?
Stairs, lifts, corridors, entrance halls and other common facilities can enlarge general gross area through an allocated share, but the owner cannot walk that share inside the apartment. Estimating it by dividing all common areas equally by the number of units is not correct for every project. Request the approved schedule and the project’s allocation method.
Land share, service-charge allocation and the common-area component of general gross area are also not interchangeable. Land share has a separate legal function under condominium law; expense allocation can follow the management plan and applicable rules. Do not use one figure automatically as the coefficient for another.
How should balconies, terraces, stores and parking be shown?
The clearest presentation has separate lines for enclosed net area, unit gross area, private annexes and common-area allocation. A balcony or terrace should state its size and open or enclosed status. Vague marketing phrases such as “total usable area” should be traced back to a defined project category.
- Balcony or terrace: disclose area and open/enclosed character separately; do not merge it into enclosed net area.
- Storage: verify whether it is a project and title annex, then state its net and gross area separately.
- Parking: clarify whether it is an independent unit, annex or right to use a common area.
- Garden use: distinguish ownership, annex status and allocated use of common property.
- Enclosed balcony: do not assume current physical use proves lawful enclosed net area.
How to compare two listings correctly
Listing A at 120 m² gross and Listing B at 135 m² gross does not prove B is larger. First normalise the gross definition. Then compare verified net room totals, layout efficiency, dimensions of primary living spaces, balconies, storage and circulation. A poorly shaped 105 m² net home with excessive corridors can be less practical than a well-planned 98 m² net home.
Your comparison sheet should include verified net area, unit gross, total gross, general gross, balcony/terrace, annex, net efficiency, price per net square metre, service charge and renovation need. This removes the headline marketing figure from its privileged position.
Reviewing the plan and evidence with property advisers can help identify comparable units and repeated marketing conventions. Adviser experience does not replace an approved project, technical measurement or independent legal review; it helps direct the right questions to the right specialist.
What should an off-plan contract state?
When buying before completion, a physical survey may not yet be possible. A contract that says only “140 m²” creates avoidable ambiguity. It should show net area, unit gross area, annex gross area, total gross area, allocated common area and general gross area on separate lines, with a dimensioned unit plan attached.
- State which regulation and approved project revision govern the area definitions.
- Fix the independent unit number, floor, orientation and exact plan type.
- Have a lawyer review the permitted tolerance and price remedy for an area shortfall.
- Show balconies, terraces, storage, parking and garden rights in separate schedules.
- Define limits on project changes and how the buyer must be notified.
- Provide a handover measurement, objection period and independent inspection mechanism.
These clauses are not solved by handwriting a number on the final page of a standard form. Consumer law, preliminary property sales, contract law and project permissions may require specialist review. The legal effect of an area difference depends on the contract, representation, evidence and rules applicable to the transaction.
Ten common area-calculation mistakes
- Not naming the gross category: unit gross and general gross are treated as identical.
- Using a fixed percentage: net is assumed to be 80% of every gross figure.
- Adding balcony to net: an open area is merged with enclosed clear space.
- Treating common area as private: an allocated stair or lift share is presented as internal space.
- Adding an undocumented store: practical use is mistaken for legal annex status.
- Using the listing as an official document: marketing copy overrides the approved plan.
- Checking an obsolete drawing: revision and existing condition are not matched.
- Dividing price by general gross only: the unit price is made to appear artificially low.
- Treating a site survey as legal registration: physical occupation is confused with a lawful right.
- Ignoring layout quality: circulation loss and room geometry are overlooked.
Final checklist before buying
- Is every square-metre figure in the listing labelled with its area category?
- Are net, unit gross, annex, total gross and general gross stated separately?
- Have you seen the dimensioned approved floor plan and latest revision?
- Are differences between the existing layout and approved project marked?
- Are balcony, terrace, storage, parking and garden rights documented separately?
- Is the source and allocation method of the common-area share explained?
- Have you calculated net-use efficiency and price per verified net square metre?
- Have at least two comparable homes been normalised to the same definition?
- Does the contract agree with the project’s area schedule?
- Has a major discrepancy been reviewed by an architect, valuer and, where necessary, a lawyer?
Frequently asked questions
What is a good gross-to-net ratio?
There is no universal ideal. Compare similar building and layout types using the same gross category. Low apparent efficiency may reflect excessive shared facilities or poor planning, but it may also arise simply because general gross area was used as the denominator.
Can I learn net area from the title deed?
A title document alone does not always provide a directly comparable verified net figure. Review the approved architectural project, area schedule and municipal file and, when necessary, commission an on-site technical survey. Do not treat a portal or listing field as conclusive without its source document.
Is a balcony included in net square metres?
Under the stated regulatory definition, balconies and similar spaces with at least one open side are not part of net unit area. Their size and utility should be disclosed separately. Enclosing a balcony later does not by itself prove that it became lawful enclosed net area.
Can I estimate gross as net plus 20%?
No. That is only a rough and unreliable shortcut. Without the building envelope, wall treatment, voids, annexes and common-area schedule, a fixed multiplier cannot establish gross area.
Why is price per net square metre useful?
It relates price to verified enclosed space the household can actually use. It still does not capture layout, balcony, storage, orientation, floor, structural condition or location. It is a comparison baseline, not a complete valuation.
What should I do if the listing and measurement differ?
First confirm that both figures use the same area definition. Then document the approved plan, contract, area schedule and survey method. Request a written explanation and obtain independent technical and legal advice before making a purchase or claim.
Is a project with a large common-area share bad?
Not automatically. Safe circulation, lifts, reception, technical rooms and useful facilities can have value. The allocation, service cost and marketing description must be transparent. General gross area should not be represented as enclosed net space.
Is higher net efficiency always better?
No. An efficient percentage can coexist with cramped circulation, weak storage or insufficient common facilities. Quality comes from an appropriate balance of usable room geometry, safe building circulation, storage, cost and accurate disclosure.
Conclusion: compare the name of the area before the number
The arithmetic of gross and net area is simple; the definition is the real work. Subtracting net from unit gross explains the difference inside the apartment envelope. Subtracting net from general gross also captures private annexes and allocated common areas. Both answers may be mathematically correct, but they answer different questions.
For every candidate property, list net area, unit gross, annex, total gross, common-area allocation and general gross on separate lines. Calculate net efficiency and price per verified net square metre, then reconcile the numbers with the approved project and current condition. This article is general information, not a technical survey, valuation or legal opinion. For a structured comparison of plans and property information, you can contact us; engage the relevant independent specialists for any material discrepancy.