1,200 Square Feet, 33.7 Pyeong: Why Overseas Listings Don't Compare Directly

The math is universal; what counts as "the area" isn't

Converting square meters to square feet is exact, fixed arithmetic everywhere — 1 square meter is always about 10.7639 square feet, based on the international definition of the foot (1 ft = 0.3048 m). What isn't universal is which square footage a country's listings actually report. A Korean apartment's advertised size is usually its 공급면적 (supply area): the unit's exclusive area plus a share of shared corridors, stairwells and lobbies. A U.S. single-family home or condo listing, by contrast, is typically just the interior of the unit — no added share of hallways or lobbies.

So a straight unit conversion (multiply by 10.7639, or divide pyeong by roughly 3.3) gets you the right number, but not automatically an apples-to-apples comparison of usable space, because the two countries are converting differently-defined things.

What your U.S. listing's square footage actually contains

For loans sold to Fannie Mae, appraisers must measure a home's gross living area (GLA) using the ANSI® Z765-2021 standard: finished, heated, above-grade space only, measured to the exterior wall surface, with basements, garages and unheated porches excluded regardless of how nicely they're finished. That's a different measurement basis than Korea's exclusive-area rule, which is measured to the interior wall surface — so even a genuinely identical two numbers won't be exactly the same floor plan.

The square footage you see on Zillow, Redfin or an MLS listing is a separate figure. It's often carried over from a county tax-assessor record or a previous listing agent's estimate rather than freshly measured, and markets vary in whether they fold in a finished basement or garage. That's why an appraiser's GLA and a listing's advertised square footage can disagree by a meaningful margin on the same house.

Reading a commercial lease: usable vs. rentable square feet

Home sales don't use anything like Korea's exclusive-to-supply ratio, but commercial office and retail leasing does have a close cousin: the load factor, defined by the ANSI/BOMA Z65.1 standard. Usable square feet (USF) is the space inside your suite; rentable square feet (RSF) is USF plus a pro-rata share of the building's shared lobbies, corridors and mechanical rooms — structurally the same idea as Korea's exclusive area plus shared common area.

Industry sources commonly cite a load factor of about 10%–25%, which works out to a usable ratio of roughly 80%–91%. At the midpoint (about 87%), 10,000 usable sq ft bills as about 11,494 rentable sq ft — the number your rent is actually calculated on. Ask for the building's specific load factor before signing; it varies a lot by building age, layout and how much shared amenity space it has.

A short checklist before you compare two listings

Whether you're sizing up an overseas apartment ad or a domestic office lease, the same habit applies: confirm what the number in front of you actually measures before comparing it to a different country's or property type's number.

• Buying a U.S. home: ask whether the quoted square footage is the appraiser's ANSI GLA or an unverified MLS/assessor figure.
• Comparing to an overseas apartment: check whether that country's advertised size already includes a common-area share (Korea and mainland China both do; the U.S. typically doesn't for home sales).
• Signing an office or retail lease: ask for the specific load factor in the lease or the building's BOMA measurement report — don't assume the industry-typical 80%–91% range applies to your building.

Common questions