1. What Is Floor Area Based on Official Measurements?
In our previous articles ( Commercial Rent Area Calculation Using the BOMA Standard — Example for One Floor, Commercial Area Calculation According to BOMA — Part 2: Recalculation After Space Reconfiguration ), we explored how commercial space is calculated using the BOMA standard — from drawings to final results across multiple scenarios.
Now we want to explain how BOMA-calculated area differs from floor area based on official floor plans, what coefficients are involved, and what challenges landlords face when leasing commercial properties.
The official floor plan area (often used in legacy systems) is a physical measurement of the space. It includes all geometric details: niches, wall thicknesses, columns — anything measurable with a tape measure.
In our example, we show a typical plan layout based on such measurements — where every structural contour is captured, but no analysis of usage, access, or shared areas is applied.
On the floor plan below, we see areas based on official floor plan measurements:
- Tenant 1: 25.95 m²
- Tenant 2: 18.91 m²
- Tenant 3: 12.67 m²
- Tenant 4: 24.99 m²
- Restroom 1: 1.77 + 2.06 = 3.83 m²
- Restroom 2: 1.77 + 2.06 = 3.83 m²
- Staircase 1: 18.73 m²
- Staircase 2: 16.75 m²
- Utility room: 3.57 m²
2. Analysis Based on Official Plan Measurements
The total measured area of the floor according to the official plan is 129.23 m². But how much of that area can actually be leased?
If we focus only on commercially leasable space — that is, usable offices — the following areas are rented out:
- Tenant 1 — 25.95 m²
- Tenant 2 — 18.91 m²
- Tenant 3 — 12.67 m²
- Tenant 4 — 24.99 m²
In total, only 83.52 m² is considered rentable, while the rest includes common areas, technical rooms, and circulation zones.
3. The Inconsistency of Measured Area: Rentable Space Depends on Tenant Count
Let’s imagine a situation where the entire floor is leased by a single tenant. In this case, not only the office units are included in the lease, but also the corridor (18.73 m²) and restrooms (7.66 m²).
The total leasable area becomes 109.91 m² instead of 83.52 m² — just because there’s only one tenant instead of multiple. That’s an increase of over 31% caused solely by the leasing scenario.
This leads to unequal conditions and complicates planning. In effect, the area based on official measurements becomes unstable, which affects:
- budget forecasting
- revenue planning
- investment analysis
For instance, the space occupied by Tenant 3 (12.67 m²) could be converted into a shared dining or break area for all tenants. That would improve infrastructure, but the officially measured leasable area would decrease.
In contrast, calculations based on the BOMA standard offer a consistent approach: the total floor area remains 131.05 m² regardless of how space is divided, used, or reassigned.
This gives landlords a clear and stable figure to work with — for planning, budgeting, reporting, and pricing. That’s the core benefit of the BOMA methodology.
4. Coefficients Between BOMA and Official Measurements: How Different Are They?
Our example clearly shows that the ratio between areas measured according to the official plan and those based on the BOMA measurement line varies significantly depending on the type and location of the space:
| Unit | Official Plan Area (m²) | BOMA Line Area (m²) | Ratio |
|---|---|---|---|
| Tenant 1 | 25.95 | 30.20 | 1.1638 |
| Tenant 2 | 18.91 | 21.19 | 1.1206 |
| Restroom 1 | 3.83 | 4.71 | 1.2298 |
| Restroom 2 | 3.83 | 4.71 | 1.2298 |
| Tenant 4 | 24.99 | 28.52 | 1.1413 |
| Corridor | 18.73 | 21.90 | 1.1692 |
| Utility Room | 3.57 | 5.00 | 1.4006 |
| Tenant 3 | 12.67 | 14.82 | 1.1697 |
| Staircase | not included in either calculation | ||
| Total | 112.48 | 131.05 | — |
The average ratio between the two methods is approximately 1.2030. When you apply this factor to the total official plan area (129.23 m²), the difference is an additional 4.27 m² — more than 3%.
This discrepancy is not random — it’s influenced by the unit’s location, surrounding elements (like shared walls with corridors or stairs), and its functional type.
If this still doesn’t convince you — let’s continue and go deeper.
5. Comparing BOMA Calculations and Official Floor Plan Areas
Let’s take data from a previous article and compare area values based on official floor plans with those calculated using the BOMA methodology. We analyzed two allocation scenarios — and in both cases, BOMA produced the same total results, with only the distribution coefficients changing.
| Unit | Official Area (m²) | BOMA Line Area (m²) | BOMA 1 (m²) | BOMA 2 (m²) | Official → BOMA 1 | Official → BOMA 2 |
|---|---|---|---|---|---|---|
| Tenant 1 | 25.95 | 30.20 | 41.78 | 43.78 | 1.6100 | 1.6871 |
| Tenant 2 | 18.91 | 21.19 | 29.31 | 30.72 | 1.5500 | 1.6245 |
| Restroom 1 | 3.83 | 4.71 | — | — | — | — |
| Restroom 2 | 3.83 | 4.71 | — | — | — | — |
| Tenant 4 | 24.99 | 28.52 | 39.45 | 35.07 | 1.5786 | 1.4034 |
| Corridor | 18.73 | 21.90 | — | — | — | — |
| Utility Room | 3.57 | 5.00 | — | — | — | — |
| Tenant 3 | 12.67 | 14.82 | 20.51 | 21.48 | 1.6188 | 1.6953 |
| Total | 112.48 | 131.05 | 131.05 | 131.05 | — | — |
We can clearly see that the total BOMA-calculated floor area remains constant — 131.05 m². Only the internal distribution among tenants varies.
Trying to establish a universal formula between official plan measurements and BOMA results is a dead end. Why? Because BOMA is not just arithmetic — it’s a transparent and equitable framework for distributing rentable space.
The total BOMA floor area stays stable at 131.05 m² regardless of the scenario. The only thing that changes is how the space is allocated.
Official plan data serves its purpose — it helps identify and register physical space. But it cannot serve as the basis for calculating true rentable area.
BOMA is more than just numbers — it’s a structured, consistent system that delivers predictable, fair outcomes for both landlords and tenants. No floating values. No surprises.
And finally — if you want to calculate areas with confidence, use our Facility platform. Fast online tools, a trusted methodology, and the option to calculate spaces on your own or with our expert help.