Gross vs. Net Area When Leasing an Office: How to Convert Correctly Before Signing

Two floor plates are both listed as "300 sqm," but once you actually lay out seating, one fits 55 desks while the other only fits 42. The gap doesn't come from good or bad design — it comes from a business comparing the wrong type of area. Converting Gross and Net area correctly when leasing an office requires distinguishing three concepts clearly: the Gross area a broker quotes, the Net usable area you actually get, and the building's efficiency ratio — these three numbers directly determine the fit-out budget per staff member, and mismatching them is the most common reason a business signs a lease only to discover afterward that it doesn't fit their team.

Why the Same Quoted Area Fits Different Headcounts

Most broker listings quote Gross Floor Area (GFA) or Leasable Area — a figure measured to the centerline of the exterior wall, without deducting the structural elements and building services that sit inside that boundary. The actual area available for desks, cabinets and circulation is meaningfully smaller once you subtract structural columns, service risers (electrical, plumbing, ventilation), the elevator core, fire-code egress corridors, and the mandatory clearance around all of these elements. The gap between Gross area and real usable area typically runs 15-30%, depending on each building's core design — and this is exactly why two floor plates quoted at the same area can seat different headcounts once you actually lay out furniture.

Distinguishing Gross, Net and Usable Area

Gross Area — the Figure on the Lease

Gross area (or Gross Leasable Area) is measured to the centerline of the exterior wall or the edge of the curtain wall glazing, and is usually the only figure that appears on the lease contract and the landlord's rate card. The rental rate (VND/m²/month) is also calculated on this Gross area, meaning a business pays for square meterage it can't actually use for desks.

Net Area — Gross Minus the Load-Bearing Envelope

Net area excludes the thickness of the exterior wall, curtain-wall glazing and main load-bearing structure, measured to the inner face of the wall. This figure is closer to reality but still doesn't reflect what can actually be furnished, since it hasn't yet deducted the building-services items scattered throughout the floor plate.

Net Usable Area — the Number That Determines Seat Count

Net Usable Area is Net area after further deducting structural columns, service risers, the elevator/stair core if it sits within the leased boundary, internal fire-code egress corridors, and the minimum clearance required around all of these elements to keep circulation paths clear. This is the figure to use when calculating desk count, meeting rooms and other functional items — not the Gross figure printed on the lease.

Efficiency Ratio and How to Read It Correctly During a Site Survey

Efficiency Ratio (sometimes expressed inversely as Loss Factor) is calculated as: Efficiency Ratio = Net Usable Area ÷ Gross Area × 100%. Grade A office buildings with a centralized, well-designed services core and elevator bank typically achieve 78-85% efficiency. Grade B, Grade C buildings or buildings converted from another use can drop to 65-75% efficiency due to a less optimized services core or denser structural columns. A 10-percentage-point efficiency gap on a 300 sqm floor plate equals roughly 30 sqm of usable area — enough for 5-6 more seats or a mid-size meeting room.

When surveying a floor plate, ask the landlord or broker for an as-built CAD drawing showing column positions, service risers and the elevator core — don't rely on a verbal Gross-area figure or a marketing rendering, which doesn't accurately reflect the real technical elements inside the space.

Converting Usable Area Into Actual Seat Count

Area Standards by Operating Model

The area standard per staff member changes with the office operating model. A traditional model with one fixed desk per person typically runs 4-6 m² of usable area per staff member, already including a base allowance for circulation and shared space. A hybrid model using desk-sharing at a 0.6-0.8 desk-to-person ratio can bring that down to 3-4.5 m² per person, calculated on total headcount (not on the number of physical desks), since part of the area is freed up by not needing a fixed desk for the entire team.

A Worked Example

For a 300 sqm Gross floor plate with a surveyed efficiency ratio of 78%, Net Usable Area comes out to 234 sqm. Applying a 5 m²/person standard for a traditional office model, this floor plate seats roughly 46-47 people once you deduct further area for meeting rooms, pantry and reception (typically 15-20% of the remaining usable area). This is why a quick calculation based only on Gross area divided by an m²/person standard always overstates seat count versus a detailed layout plan — sometimes by 15-20%. For area standards by specific headcount (10, 20, 50, 100 staff), see our article on office space standards by headcount as a quick cross-check before surveying an actual floor plate.

Common Errors When a Business Estimates Area Without a Site Survey

Three of the most common errors when a business estimates area on its own without a detailed as-built drawing: first, using Gross area instead of Net Usable Area to calculate seat count, which overstates capacity by 15-30%; second, overlooking column positions and density, which means a paper layout can't actually be built because a column sits right where a desk cluster was planned; third, failing to account for the mandatory clearance around fire exits and egress corridors, which puts the layout in violation of fire-code requirements at final inspection.

These errors can only be caught and fixed with an accurate as-built CAD drawing combined with an on-site survey — they can't be reliably estimated from a quoted area figure and marketing photos from a broker.

Not sure how many seats this floor plate can fit? What will the total interior fit-out cost run? Send Enter Office your CAD file or PDF floor plan. We'll put together a free Test Fit (preliminary space plan) within 48 hours to help you make an accurate leasing decision.

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A Leasing Decision Should Rest on a Test Fit Drawing, Not the Quoted Area

Calculating office area accurately always starts from an as-built drawing, not the Gross figure on a rate card. Efficiency ratio, structural column positions, and the m²/person standard for the chosen operating model are three variables that must go into the equation before a business puts down a deposit on a floor plate. Enter Office runs site surveys and builds Test Fit plans from real CAD drawings, so a business can see the actual seat count and layout before signing a lease — instead of relying on a quoted area figure alone.