The formula
Calculations run in your browser. Displayed values are rounded, while intermediate calculations keep their full precision.
What this estimate assumes
- Square foot, square meter and acre conversions are exact mathematical ratios (1 ft = 0.3048 m per the international yard-and-pound agreement), not estimates.
- For U.S. single-family homes and condos, the listed square footage is normally just the interior finished space — unlike Korea or mainland China, there is no standard common-area add-on baked into a home-sale listing. Appraisals for loans sold to Fannie Mae must additionally follow the ANSI® Z765-2021 standard for gross living area (GLA), which counts only finished, heated, above-grade space measured to the exterior wall surface — a different measurement basis from Korea's exclusive-area rule, which is measured to the interior wall surface.
- MLS and public-record square footage (as shown on sites like Zillow or Realtor.com) is often copied from a prior listing or tax assessor record without a fresh measurement, so it can differ from an appraiser's ANSI GLA by a meaningful margin.
- The usable-to-rentable 'load factor' concept (usable area plus a pro-rata share of common areas like lobbies and hallways) is a commercial office/retail leasing standard defined by ANSI/BOMA Z65.1, not a residential home-sale concept. Typical load factors run about 10%–25% (a usable ratio of roughly 80%–91%); this calculator's 80–91% typical range and 87% default reflect that industry-cited range, not a law or fixed regulation.
- Pyeong (1 pyeong ≈ 3.305785 sq m) is included only as a reference unit for reading Korean, Japanese or Taiwanese property listings — it is not a U.S. unit.
A quick reality check
A 1,200 sq ft U.S. listing
That's about 111.5 square meters, or roughly 33.7 pyeong if you're comparing it to a Korean apartment ad.
10,000 sq ft of usable office space at an 87% usable ratio
The rentable square footage you'd be billed for is about 11,494 sq ft — roughly 1,494 sq ft of shared lobbies, corridors and mechanical space allocated to your lease.
Common questions
Does my home's listed square footage already include hallways and shared space?
Usually not. Unlike many overseas apartment listings, U.S. single-family and condo square footage is typically just the interior of your unit, with no added share of hallways or lobbies.
Why does an appraiser's square footage sometimes differ from the MLS listing?
Appraisers for loans sold to Fannie Mae must follow the ANSI Z765-2021 measuring standard, which excludes basements, garages and any unheated space from gross living area — while MLS or public-record figures are often carried over from an earlier, unverified source.
Is the 'load factor' relevant if I'm just buying a house?
Not usually. It's a commercial office and retail leasing concept. It becomes relevant if you're leasing office or retail space, or comparing a U.S. commercial lease to a Korean or Chinese building's common-area ratio.
What's a reasonable usable ratio to expect in an office lease?
Industry sources commonly cite a load factor of about 10%–25%, which works out to a usable ratio of roughly 80%–91%. Buildings vary — ask for the specific figure in the lease or building's BOMA measurement report.