Ken Calculator – Loan calculator

Japanese Ken (間) Area Calculator

Room Length (Ken):

Room Width (Ken):

Measurement Variation: Standard / Inaka-ma (1.818m) Kyoma / Kyoto Style (1.91m) Chukyo-ma (1.7m)

Calculation Results:

Total Tsubo (坪) 0

Tatami Mats (畳) 0

Square Meters (m²) 0

Understanding the Ken Measurement System

The Ken (間) is a traditional Japanese unit of length, historically used in architecture and land measurement. While Japan adopted the metric system decades ago, the Ken remains vital in modern real estate and construction, particularly when calculating room sizes and planning layout for Tatami mats.

The Math Behind the Ken

A single Ken is roughly equivalent to 1.818 meters (about 6 feet). However, it is important to note that the exact length of a Ken can vary by region. The three most common variations are:

Inaka-ma: The modern standard used throughout most of Japan (1.818 meters).
Kyoma: The Kyoto style, often found in Western Japan, where the Ken is slightly longer (1.91 meters).
Chukyo-ma: Used primarily in the Nagoya region (roughly 1.7 to 1.82 meters).

What is a Tsubo?

When you multiply one Ken by one Ken, you get a unit of area called a Tsubo (坪). This is the primary unit used to describe land size in Japan.

Formula: Area (Tsubo) = Length (Ken) × Width (Ken)

Relationship with Tatami Mats (Jo)

In interior design, room sizes are often described by how many Tatami mats (畳 or Jo) can fit in the space. In standard modern construction, 1 Tsubo is exactly equal to 2 Tatami mats. Therefore, a 6-mat room is roughly 3 Tsubo in size.

Practical Example

If you have a traditional Washitsu (Japanese-style room) that measures 2 Ken by 3 Ken:

Tsubo Calculation: 2 Ken × 3 Ken = 6 Tsubo.
Tatami Count: 6 Tsubo × 2 = 12 Tatami mats.
Metric Area: 6 Tsubo × 3.3057 ≈ 19.83 square meters.

function calculateKen() { var length = parseFloat(document.getElementById('kenLength').value); var width = parseFloat(document.getElementById('kenWidth').value); var kenValue = parseFloat(document.getElementById('kenType').value); if (isNaN(length) || isNaN(width) || length <= 0 || width <= 0) { alert("Please enter valid positive numbers for length and width."); return; } // 1 Ken (Standard) = 1.818 meters // Area in Tsubo = Length(Ken) * Width(Ken) var tsubo = length * width; // 1 Tsubo = 2 Tatami mats var tatami = tsubo * 2; // Area in square meters: (Length * KenValue) * (Width * KenValue) var sqm = (length * kenValue) * (width * kenValue); // Display Results document.getElementById('resTsubo').innerHTML = tsubo.toFixed(2); document.getElementById('resTatami').innerHTML = tatami.toFixed(1); document.getElementById('resSqm').innerHTML = sqm.toFixed(2) + " m²"; document.getElementById('kenResult').style.display = 'block'; }