Actualizado July 2026

Building Square Footage Calculator

Measure the footprint, multiply by the number of floors, and see the gross building area — plus how it differs from the usable and rentable space you lease.

100% gratis — sin registro
Resultados instantáneos en tiempo real
Los datos nunca salen de tu navegador
Usada por propietarios y contratistas

Unidades

Largo

Ancho

Área total

1,938ft²

Metros cuadrados

180 m²

Yardas cuadradas

215.3 yd²

Qué significa

To calculate the square footage of a building, measure the footprint — length × width in feet — and multiply by the number of floors. An 80 ft × 50 ft footprint is 4,000 sq ft per floor, so a 3-story building is 12,000 sq ft gross. Gross building area is measured to the outside walls; usable and rentable area, measured inside, is smaller.

Fórmula y guía

Cómo se calcula

A building's gross area is its footprint multiplied by the number of floors. Measure to the outside face of the exterior walls, and split any irregular footprint into rectangles you can add together.

1Measure the footprint length and width in feet at ground level, to the outside of the exterior walls.
2Multiply length × width to get the footprint area (the area of one floor).
3For an irregular footprint, split it into rectangles, calculate each, and add them together.
4Multiply the footprint area by the number of floors to get the gross building area.

Ejemplo resuelto

Míralo en números

Footprint (80 ft × 50 ft)	4,000 sq ft
Number of floors	3
Gross building area (4,000 × 3)	12,000 sq ft
Usable area (≈85%)	≈ 10,200 sq ft

A 4,000 sq ft footprint across 3 floors gives 12,000 sq ft of gross building area.

Precisión y supuestos

The footprint is measured to the outside face of the exterior walls, so gross area includes wall thickness.
Every floor is assumed to share the same footprint; setbacks or partial floors are measured separately.
Basements, mezzanines, and enclosed structural areas count toward gross building area.
Open, unroofed areas such as courtyards and parking lots are excluded from the building square footage.

Consejos y reglas clave

Gross Building Area is measured to the outside walls across all floors; usable area is the interior space occupants actually occupy.
Multiply the footprint by the floor count — a 4,000 sq ft footprint on 3 levels is 12,000 sq ft, not 4,000.
Rentable area falls between gross and usable: it adds a tenant's share of common areas like lobbies and corridors.
The load (or core) factor is rentable ÷ usable; BOMA standards define how usable, rentable, and gross are measured for leases.

Casos de uso

Para quién es esta calculadora

Commercial leasing

Landlords quote rent as $/sq ft of rentable area, so gross, usable, and rentable figures drive the lease.

Construction estimating

Contractors price new builds and renovations per square foot of gross floor area to scope budgets.

Facilities planning

Facility managers use usable area to plan workstations, occupancy, and space allocation per employee.

How to calculate the square footage of a building

Calculating a building's square footage starts at the ground: measure the footprint, which is the outline the building covers on the site. Take the length and width in feet, measured to the outside face of the exterior walls, and multiply them for the area of a single floor. A rectangular 80-by-50-foot building has a 4,000-square-foot footprint. Multiply that footprint by the number of floors and you have the gross building area — for three identical floors, that's 12,000 square feet. Our calculator above handles the multiplication; you supply the dimensions.

Real buildings are rarely perfect rectangles. When the footprint is L-shaped, T-shaped, or stepped, break it into simple rectangles, calculate each one, and add the results. This is the same rectangle-splitting approach you'd use to measure a warehouse or an oddly shaped room — just applied to the whole building outline. If different floors have different footprints, such as a tower rising above a wider base, measure each floor separately and sum them rather than assuming every level is identical.

Gross, usable, and rentable area — what the difference means

Not all square footage is the same, and the distinction matters most when money changes hands. Gross Building Area is the total measured to the outside walls, including structural walls, mechanical rooms, and shared spaces. Usable area is the interior space a tenant actually occupies — the offices, workrooms, and floor an employee stands on. Between the two sits rentable area, which takes a tenant's usable space and adds a proportional share of common areas like lobbies, corridors, and restrooms.

The relationship between rentable and usable is captured by the load factor (also called the core factor): rentable area divided by usable area. A load factor of 1.15 means a tenant pays for 15% more space than they exclusively occupy, covering their share of the building's common areas. The BOMA (Building Owners and Managers Association) standards define exactly how each of these areas is measured, giving landlords and tenants a common language so a quoted $/sq ft rent is comparing like with like across an office space.

Why building square footage drives cost

Square footage is the unit that turns a building into a budget. Commercial leases are almost always quoted per square foot per year, so a 12,000-square-foot space at $25 per square foot is a $300,000 annual rent before any adjustments. Construction and renovation estimates work the same way, pricing per square foot of gross floor area to scope everything from framing to finishes.

Once you know the gross area, multiplying by a rate makes the number actionable — the same logic our square footage cost calculator applies to any project. Whether you're comparing lease offers, estimating a build, or planning how many people a floor can hold, an accurate square footage figure, and a clear sense of whether it's gross, usable, or rentable, keeps every downstream calculation honest.

Calculadoras relacionadas

Combina bien con

Warehouse Office Cost Room

Preguntas

Preguntas sobre la calculadora de Building

Measure the footprint — length × width in feet to the outside of the exterior walls — and multiply by the number of floors. An 80 ft × 50 ft footprint is 4,000 sq ft per floor, so a 3-story building is 12,000 sq ft gross. For an irregular footprint, split it into rectangles and add them together.

Gross building area is measured to the outside walls and includes every floor, structural walls, and mechanical space. Usable area is the interior space a tenant actually occupies. Rentable area sits between them, adding a tenant's share of common areas. Usable is typically 80–90% of gross, depending on the building's efficiency.

Yes. Gross building area is the footprint of each floor added together. A single-story 4,000 sq ft footprint is 4,000 sq ft, but the same footprint over three floors is 12,000 sq ft. Basements, mezzanines, and enclosed levels count; open courtyards and parking lots do not.

The load factor (or core factor) is rentable area divided by usable area. A factor of 1.15 means you pay for 15% more space than you exclusively occupy, covering your share of lobbies, corridors, and restrooms. BOMA standards define how usable, rentable, and gross areas are measured so leases are comparable.

Desde el blog