Reading Japanese Floor Plan Notation: 1K, 1DK, 1LDK, Tatami Mats, and Tsubo

The short version

The number is bedrooms; the letters describe the extra room. R = room, K = kitchen, D = dining, L = living. A "1LDK" is one bedroom plus a combined living-dining-kitchen room, not two rooms.
Whether that extra room gets labeled K, DK, or LDK depends mostly on its own floor area, not on the apartment as a whole — roughly under 4.5 jō is a K, 4.5–8 jō is a DK, and 8+ jō is an L(D)K, though the exact cutoff varies a little by listing site.
Jō (also written 畳 or "tatami mat") is the unit room sizes are quoted in. For advertising purposes, Japan's real estate fair trade rules require 1 jō to be counted as at least 1.62 m² — but an actual physical tatami mat's size still varies by region (Edo-ma, Kyo-ma, danchi-ma), so two "6-jō" rooms in different buildings aren't always identical.
Tsubo (坪) is a separate, larger unit mostly used for whole-apartment or land area: 1 tsubo = 2 jō ≈ 3.31 m².
Other letters worth knowing from a listing: SB (shoe box, a built-in shoe cabinet by the entrance), CATV (cable TV wiring is present), and whether gas is listed as toshi gas (piped city gas) or propane/LP gas (tank-supplied, usually pricier per unit).

A listing page shows "1LDK・45.3㎡" next to a thumbnail floor plan too small to read clearly, and the natural next thought is: is that one bedroom or two, and is 45.3 square meters roomy or cramped? Both questions have a fairly mechanical answer once the notation clicks, and knowing it before the viewing means you can rule out listings that don't fit — instead of discovering the layout in person.

The letters: what R, K, DK, and LDK mean

1R — one room

A studio: one open room with no partition between the sleeping and living space. The kitchen is usually a small counter along one wall rather than a separate area, and the bath is often a "unit bath" (toilet, sink, and tub molded into one small pre-fab room).

Smallest and usually cheapest single-person option

1K — one room + kitchen

One bedroom plus a kitchen area separated by a door or partition, where the kitchen space itself is small (as a rule of thumb, under about 4.5 jō). The separation mostly matters for cooking smells and sound, not floor area.

A step up from 1R when you want the kitchen behind a door

1DK — one room + dining kitchen

Same one-bedroom shape as a 1K, but the kitchen/dining room is bigger — roughly 4.5 to 8 jō — enough to fit a small table, not just a counter. Real estate sites don't apply the exact cutoff identically, so treat it as a size signal rather than a fixed rule.

Room enough to eat somewhere other than the kitchen counter

1LDK, 2LDK, and up

The L adds a living-room function to the dining/kitchen room once it passes roughly 8 jō, making it big enough to function as a proper living room too. The number in front still counts separate bedrooms only — a "2LDK" is two bedrooms plus one shared living-dining-kitchen room, not three rooms.

Typical shape for a couple, roommates, or a small family

None of these thresholds are enforced by law the way the jō-to-square-meter rule below is — they're conventions that most listing sites and agencies follow closely enough to be a reliable size signal, but a specific listing can occasionally sit right on the boundary and get labeled either way.

The numbers: jō, tsubo, and square meters

A jō (also spelled jo, or written 畳) is one tatami mat's worth of floor area, and it's the unit used to describe individual room sizes even in rooms that don't have actual tatami flooring. The twist: a physical tatami mat isn't one fixed size across Japan. The Edo-ma standard common in and around Tokyo runs about 1.55 m² per mat, the Kyo-ma standard used in the Kansai region is closer to 1.82 m², and the smaller danchi-ma size used in older public housing comes in around 1.45 m². For advertising purposes, Japan's real estate fair trade rules sidestep that regional gap. They require listings to count 1 jō as no less than 1.62 m², calculated from the room's total floor area divided by however many jō it's advertised as. So a listed "6 jō" room is guaranteed to be at least about 9.7 m², even in a room with no physical tatami mats in it at all.

Unit	Roughly equals	Where you'll see it
1 jō (畳)	≥ 1.62 m² (advertising minimum); a real mat varies ~1.45–1.82 m² by region	Individual room sizes on a floor plan
1 tsubo (坪)	2 jō ≈ 3.31 m²	Whole-unit or land area, especially older listings
1 m² (㎡)	≈ 0.3025 tsubo ≈ 0.62 jō	The "専有面積" (exclusive floor area) figure on modern listings

In practice, the number worth anchoring on is the total exclusive floor area in square meters (専有面積, senyū menseki) printed near the top of most listings — it's the one figure that doesn't shift with regional tatami sizing. Treat the jō count per room as a useful ratio for comparing rooms within the same listing, not as a precise, universal measurement you can convert with one fixed formula.

Other letters and abbreviations on a listing

Abbreviation	What it means
SB	Shoe box — a built-in shoe cabinet near the entrance, not a separate room
CATV	The building has cable TV wiring already run to the unit
都市ガス (toshi gas)	Piped city gas, generally cheaper per unit than the alternative below
プロパン / LPガス (propane/LP gas)	Tank-supplied gas, common in areas without a city gas main; typically a higher per-unit rate
専有面積 (senyū menseki)	The unit's own exclusive floor area in m² — the figure to compare across listings

The gas line is worth a second look before you get attached to a listing on price alone: propane/LP gas costs more per unit to run than piped city gas in most areas, so an otherwise-cheap apartment on propane can end up costing more monthly once utilities are added in.

Where this guide stops

This page explains the notation, not a specific building. Actual room shapes, ceiling height, storage, and how "livable" a given jō count feels in person vary by building and can't be judged from letters and numbers alone — the layout thumbnail and, ideally, an in-person or video viewing still matter. It also isn't real estate brokerage or legal advice, and it doesn't recommend any specific agent, portal, or property.

Related guides

Once a listing's shape and size make sense, the next questions tend to be about the format of renting itself and what it takes to qualify. Our comparison of share house, apartment, monthly mansion, and guest house covers which format fits a given budget and paperwork situation. Our guide to rental guarantors in Japan covers the screening step that comes after you pick a unit, and our security deposit guide covers what you get back at the other end of the lease. Once you've signed and have keys in hand, our move-in checklist covers what to set up in the first week.

This article provides general information only and is not real estate brokerage or legal advice. Floor-plan labeling conventions and actual room dimensions vary by listing site, agency, and building, and the fair-trade minimum described above governs advertising, not every physical tatami mat in every room; confirm the actual layout and measurements with the listing agent or during a viewing before relying on them. See our disclaimer for more.

Sources

Confirmed via search engine results on 2026-09-12. This working environment's direct fetch of the domains below was blocked by the network's egress policy while writing this article, so the notation conventions, size thresholds, and unit conversions above are cross-checked across multiple independent sources rather than a single direct read of one source. Room-type letter/size cutoffs in particular are described by sources as a common convention rather than a single codified rule, and this article presents them the same way.

Izanau — "Japanese Apartments: What's the Difference Between 1R, 1K, 1DK, and 1LDK?": izanau.com
BELONGING JAPAN — "Japanese Apartment Layouts Explained: What Does 1K And 1畳 Mean?": belongingjapan.com
PLAZA HOMES / Real Estate Japan — "Units Used to Describe the Size of Real Estate in Japan": realestate-tokyo.com
Nippon Tradings International — "Understanding Japanese Real Estate Measurement Units: A Comprehensive Guide" (regional tatami sizes — Edo-ma, Kyo-ma, danchi-ma): nippontradings.com
Tokyo Portfolio — "10 Essential Japanese Real Estate Terms You Need to Know": tokyoportfolio.com
Real Estate Japan (resources.realestate.co.jp) — "Glossary of Japanese Real Estate Terms: Keywords for Renting an Apartment" (SB, CATV, toshi gas/propane): resources.realestate.co.jp
GTN MAGAZINE — "Finding the Perfect Japanese Apartment: A Complete Guide to Floor Plans for Foreign Residents": gtn.co.jp