Fathom to Ken Converter
Convert fathoms to ken with our free online length converter.
Quick Answer
1 Fathom = 1.005941 ken
Formula: Fathom × conversion factor = Ken
Use the calculator below for instant, accurate conversions.
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Fathom to Ken Calculator
How to Use the Fathom to Ken Calculator:
- Enter the value you want to convert in the 'From' field (Fathom).
- The converted value in Ken will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Length category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Fathom to Ken: Step-by-Step Guide
Converting Fathom to Ken involves multiplying the value by a specific conversion factor, as shown in the formula below.
Formula:
1 Fathom = 1.005941 kenExample Calculation:
Convert 10 fathoms: 10 × 1.005941 = 10.05941 ken
Disclaimer: For Reference Only
These conversion results are provided for informational purposes only. While we strive for accuracy, we make no guarantees regarding the precision of these results, especially for conversions involving extremely large or small numbers which may be subject to the inherent limitations of standard computer floating-point arithmetic.
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Need to convert to other length units?
View all Length conversions →What is a Fathom and a Ken?
The Six-Foot Maritime Standard
The fathom is defined as exactly 6 feet in the imperial and U.S. customary measurement systems.
Precise equivalents:
- 6 feet (by definition)
- 2 yards (6 ft ÷ 3 ft/yd)
- 72 inches (6 ft × 12 in/ft)
- 1.8288 meters (exactly, using 1 ft = 0.3048 m)
- 182.88 centimeters
Historical basis: The arm span of an average man with arms fully outstretched, measured from fingertip to fingertip.
Arm Span Origins
Old English "fæthm":
- Primary meaning: To embrace, encircle with outstretched arms
- Secondary meaning: The distance between fingertips when arms are extended
Practical measurement: Sailors hauling in sounding lines (weighted ropes for measuring depth) would pull hand-over-hand, with each arm span representing one fathom. This created a natural counting method:
- Drop weighted line overboard
- Haul in, counting arm spans
- Number of arm spans = depth in fathoms
Standardization necessity: Since arm spans varied (5.5-6.5 feet typically), maritime commerce required a fixed standard. The British settled on exactly 6 feet, matching the standardized foot of 12 inches.
Nautical Charts and Depth Contours
Fathom lines: Nautical charts show depth contours (lines connecting points of equal depth) traditionally measured in fathoms.
Common contour intervals:
- 1, 2, 3, 5, 10 fathoms: Shallow coastal waters
- 20, 50, 100 fathoms: Coastal navigation
- 500, 1,000 fathoms: Deep ocean
Chart notation: Depths written as plain numbers on charts (e.g., "45") indicate 45 fathoms unless otherwise specified. Modern charts often include a note: "Depths in fathoms" or "Depths in meters."
Anchor Cable and Chain
Shackle: One "shackle" of anchor chain traditionally equals 15 fathoms (90 feet / 27.43 m) in the Royal Navy and many navies worldwide.
Anchoring depth rule: Ships typically anchor with a scope (ratio of chain length to water depth) of 5:1 to 7:1 for safety.
Example:
- Water depth: 10 fathoms (60 feet)
- Required chain: 50-70 fathoms (300-420 feet)
- That's 3.3 to 4.7 shackles
The Ken (間) is a traditional Japanese unit of length, primarily used in architecture and related fields. It is fundamentally defined as being equal to 6 Shaku (尺). Based on the modern standardized kanejaku Shaku (10/33 meters), the Ken is equivalent to:
- 6 * (10/33) = 60/33 = 20/11 meters
- Approximately 1.818 meters
- Approximately 5.965 feet
Historically, the Ken represented the interval between pillars in traditional Japanese buildings and served as a fundamental module for architectural design, influencing room sizes and the dimensions of elements like tatami mats.
Note: The Fathom is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Ken belongs to the imperial/US customary system.
History of the Fathom and Ken
Ancient Maritime Practices (Pre-9th Century)
Mediterranean and Northern European sailors: Ancient mariners measured rope and depth using body-based units:
- Cubit: Elbow to fingertip (~18 inches)
- Pace: Two steps (~5 feet)
- Arm span: Outstretched arms (~6 feet)
Sounding lead: A heavy weight (lead sinker) attached to a marked line, dropped overboard to measure depth. Sailors counted arm spans as they hauled the line back aboard.
Old English Documentation (9th-11th Centuries)
Earliest references: Anglo-Saxon texts use "fæthm" for measuring rope lengths and describing distances.
Beowulf (8th-11th century): The epic poem mentions "fæthmas" in describing ocean depths and ship measurements.
Viking influence: Old Norse "faðmr" (similar arm-span measurement) influenced English usage through Viking contact and trade.
Medieval Standardization (13th-15th Centuries)
Edward I (1272-1307): English law under Edward I began standardizing measurements, including the fathom at 6 feet.
Admiralty regulations: The emerging Royal Navy needed consistent rope, sail, and depth measurements for shipbuilding and navigation.
Rope making: British rope makers sold cordage by the fathom, with standard lengths for anchor cables (120 fathoms = 1 cable length in some contexts).
Age of Exploration (15th-17th Centuries)
Navigation charts: Early nautical charts (portolan charts) began incorporating depth soundings in fathoms.
Captain James Cook (1768-1779): Cook's Pacific voyages produced meticulous charts with fathom-based depth measurements. His charts became templates for British Admiralty standards.
Example - HMS Endeavour soundings: Cook's logs record depths like "15 fathoms, sandy bottom" or "No bottom at 100 fathoms" (indicating depths exceeding 600 feet).
British Admiralty Charts (19th Century)
Hydrographic Office (founded 1795): The British Admiralty Hydrographic Office systematized global nautical chart production, standardizing fathoms for depth.
Matthew Fontaine Maury (1806-1873): American oceanographer Maury collaborated with the British to create standardized depth charts using fathoms, mapping ocean currents and depths.
Cable-laying expeditions: Transatlantic telegraph cable projects (1850s-1860s) required precise fathom-based depth surveys. HMS Agamemnon and USS Niagara charted the Atlantic floor in fathoms before laying the 1858 cable.
U.S. Navy Adoption (19th-20th Centuries)
Inherited British standards: The U.S. Navy adopted British maritime practices, including fathom-based charts and anchor cable measurements.
U.S. Coast and Geodetic Survey: Founded in 1807 (originally "Survey of the Coast"), it produced nautical charts in fathoms for American waters.
World War II: Submarine warfare and amphibious operations relied heavily on fathom-based depth charts. USS submarines operated in waters charted in fathoms.
Metrication Movement (20th Century-Present)
International Hydrographic Organization (IHO, founded 1921): Recommended global adoption of metric system for nautical charts.
Gradual transition:
- 1970s-1980s: Most nations began publishing new charts in meters
- UK Admiralty: Converted most charts to meters by the 1990s
- U.S. NOAA: Many American charts still use fathoms, particularly for coastal waters
Mixed usage today: Modern electronic chart systems (ECDIS) allow display in either fathoms or meters, accommodating mariners accustomed to either system.
The concept of the Ken, like the Shaku, originated from Chinese architectural practices (where the equivalent unit is Jian 間). It was adopted into Japan along with other elements of Chinese culture and measurement systems.
- Early Use: The Ken was used early on as a standard interval in temple and palace construction. Its length, however, was not strictly fixed and could vary based on the specific building style, region, or period. It was often tied directly to the prevailing length of the Shaku.
- Standardization Attempts: Over time, particularly during the Edo period (1603–1868), attempts were made to standardize measurements. The Ken became strongly associated with architectural modules. Two prominent regional standards emerged:
- Kyōma (京間): The Kyoto module, typically based on a slightly larger Ken (often around 6.5 Shaku or based on tatami dimensions), leading to larger room sizes.
- Inakama (田舎間) / Edoma (江戸間): The rural or Edo (Tokyo) module, typically adhering more closely to the 6 Shaku standard or sometimes slightly smaller (e.g., 6.3 Shaku), resulting in slightly smaller rooms. This became more common.
- Meiji Restoration (1868 onwards): With the standardization of the Shaku at 10/33 meters in 1891, the Ken was implicitly standardized as 6 Shaku = 20/11 meters (approx. 1.818 m). This is the value generally understood as the modern Ken.
- Metrication: Although Japan officially adopted the metric system, the Ken remains a crucial unit in traditional architecture and related fields.
Common Uses and Applications: fathoms vs ken
Explore the typical applications for both Fathom (imperial/US) and Ken (imperial/US) to understand their common contexts.
Common Uses for fathoms
1. Nautical Charts and Hydrography
Depth soundings: Nautical charts mark depths in fathoms, particularly on U.S. and older British charts.
Contour lines: Lines connecting equal depths (e.g., the 10-fathom line) help mariners avoid shallow areas.
Chart abbreviations:
- fms: Fathoms
- fm: Fathom
- No bottom at 100 fms: Depth exceeds 100 fathoms (600 feet)
2. Anchoring and Mooring
Anchor scope: Mariners calculate how much anchor chain to deploy based on water depth in fathoms.
Rule of thumb: Deploy 5-7 times the water depth in calm conditions, 7-10 times in storms.
Example:
- Depth: 8 fathoms
- Calm weather scope (5:1): 40 fathoms of chain
- Storm scope (10:1): 80 fathoms of chain
3. Commercial Fishing
Net depth: Fishermen describe trawl net depths in fathoms.
Example: "Running trawl at 50 fathoms" (300 feet deep)
Fishing line: Deep-sea fishing lines measured in fathoms to target specific depths.
4. Recreational Boating and Diving
Depth sounders: Many recreational boat depth finders display fathoms (though meters and feet are increasingly common).
Dive planning: Divers reference depth in fathoms on nautical charts when planning dive sites.
5. Submarine Operations
Periscope depth: Submarines traditionally use fathoms for depth control.
Example: "Dive to 20 fathoms" (120 feet)
Historical note: WWII submarine logs recorded depths in fathoms; modern submarines use meters.
6. Maritime Literature and Tradition
Nautical expressions:
- "To fathom something" = to understand its depth (metaphorically)
- "Unfathomable" = too deep to measure or comprehend
Sailing instructions: Traditional pilot books use fathoms for approach depths and anchorage recommendations.
When to Use ken
The Ken's primary importance lies in its role as an architectural module:
- Traditional Japanese Architecture: It defines the standard bay (pillar-to-pillar distance) in the ken module system (kenshin system 間真). This dictates the layout and proportions of temples, shrines, traditional houses (minka), teahouses, and castles. Room sizes are often described in terms of tatami mats, whose standard dimensions (historically 1 Ken by 0.5 Ken) are derived from the Ken.
- Construction and Carpentry: Used for planning layouts, cutting timber, and sizing building components like fusuma (sliding doors) and shōji (screens).
- Real Estate and Land: Room sizes in Japan are often measured by the number of tatami mats they can hold (e.g., a "6-mat room" - 六畳 rokujō), which indirectly relates to the Ken. Historically, it was also used for land parcel dimensions.
- Martial Arts: The concept of distance or interval (maai 間合い) between opponents is crucial and sometimes measured or conceptualized in terms of Ken. The length of certain weapons, like the bō (staff), is often around 1 Ken (6 Shaku).
- Traditional Garden Design: Used for establishing proportions and spacing elements within Japanese gardens.
- Cultural and Historical Context: Understanding the Ken is essential for interpreting historical architectural plans, documents, and cultural descriptions of space.
Additional Unit Information
About Fathom (fath)
How many feet are in a fathom?
Exactly 6 feet = 1 fathom.
This is the defining relationship. The fathom was standardized to 6 feet during medieval English measurement standardization.
How many meters are in a fathom?
1 fathom = 1.8288 meters (exactly).
This conversion uses the international foot definition: 1 foot = 0.3048 meters (exactly).
Calculation: 6 feet × 0.3048 m/ft = 1.8288 m
Is the fathom an SI unit?
No, the fathom is not an SI unit.
It belongs to the imperial and U.S. customary systems. The SI unit of length is the meter.
International usage: The International Hydrographic Organization recommends meters for nautical charts, but fathoms remain legal and common in U.S. and some British waters.
Is the fathom still commonly used today?
Yes, in specific maritime contexts, especially in the United States.
Still common:
- U.S. NOAA nautical charts (many coastal charts)
- Recreational boating in the U.S.
- Commercial fishing fleets
- Maritime tradition and literature
Declining usage:
- International shipping (uses meters)
- Most modern navies (switched to meters)
- New chart production (increasingly metric)
Result: Fathoms persist in American waters and traditional maritime communities but are gradually being replaced by meters in international contexts.
Where does the word "fathom" come from?
From Old English "fæthm" (outstretched arms, embrace).
Etymology:
- Proto-Germanic: *faþmaz (embrace, armful)
- Old English: fæthm (span of outstretched arms)
- Middle English: fadme, fathme
- Modern English: fathom
Original meaning: The distance between fingertips when a person extends both arms horizontally—roughly 6 feet for an average man.
Verb form: "To fathom" originally meant "to measure depth with outstretched arms," later metaphorically "to comprehend deeply" (exploring the depths of understanding).
Why are anchor chains measured in shackles, not fathoms?
Both are used, but shackles are standard for large vessels.
Shackle definition: 1 shackle = 15 fathoms = 90 feet = 27.43 meters
Reason: Anchor chains are physically connected with shackle links every 15 fathoms. These physical shackles allow disconnection for maintenance and provide visual/tactile markers when deploying chain.
Usage:
- Small vessels: Anchor chain length in fathoms
- Large vessels and navies: Anchor chain length in shackles
Example: "Deploy 5 shackles" = 75 fathoms = 450 feet of chain
How deep is "full fathom five"?
5 fathoms = 30 feet = 9.144 meters.
Shakespeare's The Tempest: Ariel's song describes a drowned man lying at the bottom, 5 fathoms below the surface.
Context: 30 feet is deep enough that:
- Surface light barely reaches the body
- Free diving without equipment is challenging
- The body would be difficult to recover without specialized equipment
This depth creates the eerie, unreachable quality of Ariel's description.
Can I convert my depth sounder from fathoms to meters?
Yes, most modern depth sounders (fishfinders, chartplotters) allow unit selection.
Typical options:
- Feet
- Fathoms
- Meters
How to change (general steps):
- Access settings menu
- Find "Units" or "Depth Units"
- Select preferred unit (fathoms, feet, or meters)
- Save settings
Check manual: Specific instructions vary by manufacturer (Garmin, Lowrance, Raymarine, Furuno, etc.).
What's the difference between fathoms and cable lengths?
Both are nautical length units, but they measure different things:
Fathom:
- 6 feet / 1.8288 meters
- Primarily for depth measurement
Cable length:
- UK: 608 feet = 185.3 meters (1/10 nautical mile)
- US (historical): 720 feet = 219.5 meters (120 fathoms)
- Primarily for horizontal distance (anchor cable, ship-to-ship spacing)
Confusion: The term "cable" sometimes referred to 100 or 120 fathoms of anchor cable, but the standardized "cable length" unit differs from this.
Do submarines still use fathoms?
Historically yes, but modern submarines use meters.
World War II era: U.S. and British submarines recorded depths in fathoms (e.g., "Dive to 50 fathoms").
Modern practice:
- U.S. Navy: Switched to feet and meters for submarine operations
- International: Nearly all modern navies use meters
Reason for change: International standardization, digital instrumentation, and NATO interoperability drove metrication.
About Ken (ken)
How long is a Ken?
The modern standard Ken is defined as 6 Shaku. Using the standardized kanejaku Shaku (10/33 m):
- 1 Ken = 20/11 meters
- Approximately 1.818 meters
- Approximately 181.8 centimeters
- Approximately 5.965 feet
- Approximately 71.58 inches Historical and regional variations (like the kyōma) existed, often resulting in slightly different lengths.
How does the Ken relate to the Shaku?
The Ken is a direct multiple of the Shaku:
- 1 Ken = 6 Shaku
Is the Ken related to the Tatami mat?
Yes, very closely. The standard size of a tatami mat was traditionally defined in relation to the Ken, typically 1 Ken long by 0.5 Ken wide (though dimensions varied slightly with regional modules like kyōma and inakama). Room sizes are often measured by the number of tatami mats they contain.
Is the Ken an SI unit?
No, the Ken is not an SI unit. It is a traditional Japanese unit belonging to the Shakkanhō (尺貫法) system. The SI base unit for length is the meter (m).
Is the Ken still used today?
Yes. While the metric system is the official standard in Japan for commerce and science, the Ken remains highly relevant and actively used in:
- Traditional Japanese architecture, design, and construction.
- Carpentry and traditional crafts.
- Real estate descriptions (indirectly via tatami count).
- Martial arts contexts.
- Cultural and historical studies.
- Traditional garden design.
Conversion Table: Fathom to Ken
| Fathom (fath) | Ken (ken) |
|---|---|
| 0.5 | 0.503 |
| 1 | 1.006 |
| 1.5 | 1.509 |
| 2 | 2.012 |
| 5 | 5.03 |
| 10 | 10.059 |
| 25 | 25.149 |
| 50 | 50.297 |
| 100 | 100.594 |
| 250 | 251.485 |
| 500 | 502.97 |
| 1,000 | 1,005.941 |
People Also Ask
How do I convert Fathom to Ken?
To convert Fathom to Ken, enter the value in Fathom in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our length converter page to convert between other units in this category.
Learn more →What is the conversion factor from Fathom to Ken?
The conversion factor depends on the specific relationship between Fathom and Ken. You can find the exact conversion formula and factor on this page. Our calculator handles all calculations automatically. See the conversion table above for common values.
Can I convert Ken back to Fathom?
Yes! You can easily convert Ken back to Fathom by using the swap button (⇌) in the calculator above, or by visiting our Ken to Fathom converter page. You can also explore other length conversions on our category page.
Learn more →What are common uses for Fathom and Ken?
Fathom and Ken are both standard units used in length measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our length converter for more conversion options.
For more length conversion questions, visit our FAQ page or explore our conversion guides.
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⚖️ Metric vs Imperial
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All Length Conversions
Other Length Units and Conversions
Explore other length units and their conversion options:
- Meter (m) • Fathom to Meter
- Kilometer (km) • Fathom to Kilometer
- Hectometer (hm) • Fathom to Hectometer
- Decimeter (dm) • Fathom to Decimeter
- Centimeter (cm) • Fathom to Centimeter
- Millimeter (mm) • Fathom to Millimeter
- Inch (in) • Fathom to Inch
- Foot (ft) • Fathom to Foot
- Yard (yd) • Fathom to Yard
- Mile (mi) • Fathom to Mile
Verified Against Authority Standards
All conversion formulas have been verified against international standards and authoritative sources to ensure maximum accuracy and reliability.
National Institute of Standards and Technology — Official US standards for length measurements
Bureau International des Poids et Mesures — International System of Units official documentation
Last verified: February 19, 2026