Convert Fathom to Chain
Convert fathoms to chains instantly. 1 fathom = 0.0909090909 chain — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Chain to Fathom converter for the reverse conversion.
Units explained
Fathom
A fathom is an Imperial unit of length equal to 6 feet or exactly 1.8288 meters. It is used almost exclusively for measuring water depth in maritime contexts.
The fathom derives from the Old English word fæthm, meaning "the embracing arms" — the distance between the fingertips of a person's outstretched arms. Standardized at 6 feet in English maritime tradition.
Fathoms are used in nautical depth charts, scuba diving, oceanography, and maritime literature. Despite metrication efforts, fathoms remain common in English-language nautical charts and recreational diving.
Old English origin (predating 1066); standardized at 6 feet by English maritime tradition; fixed at 1.8288 m exactly via the 1959 International Yard and Pound Agreement.
Chain
A chain is an Imperial unit of length equal to 66 feet (20.1168 m), or exactly 4 rods or 100 links. It is the central unit in the Gunter chain-based land-survey system.
Defined by Edmund Gunter in 1620 specifically to make land-area arithmetic easy: 10 square chains = 1 acre exactly. The 66-foot length and 100-link subdivision were chosen so chain measurements could be added decimally.
Chains are the fundamental unit of legacy US public land surveys (the entire US township-and-range system uses chains). Modern survey work generally uses meters or feet, but legacy deeds remain in chains.
Invented by Edmund Gunter in 1620; standardised throughout English and American land survey; became exact via the 1959 International Yard and Pound Agreement.
Fathom to Chain conversion formula
The relationship between fathoms and chains:
To convert fathoms to chains, multiply the value in fathoms by 0.0909090909. To reverse, multiply chains by 11.
How to use this converter
Type a value into the calculator. The result in chains updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Chain to Fathom converter for the reverse direction.
Step-by-step: convert fathoms to chains
- Write down the value in fathoms (ftm).
- Multiply that value by the factor 0.0909090909.
- The product is the equivalent value in chains (ch).
- To reverse, multiply the chain value by 11.
Worked examples
Example 1 — Convert 1 ftm to ch:
1 × 0.0909090909 = 0.0909090909 ch
Example 2 — Convert 100 ftm to ch:
100 × 0.0909090909 = 9.0909090909 ch
Real-world example — Fabric purchase length
Two fathoms of fabric equals a value in chains essential for tailors and textile buyers sourcing material from international suppliers that quote in different units.
2 ftm × 0.0909090909 = 0.1818181818 ch
Real-world example — Maritime depth conversion
A 10-fathom sounding depth converts cleanly into chains. Recreational divers and sailors translate between the two units whenever they read legacy charts against modern depth-sounder displays.
10 ftm × 0.0909090909 = 0.9090909091 ch
Real-world example — Reference scenario in case of fallback
Conversion between human-scale length units is the everyday workflow of architecture, athletics, and apparel design — three of the most common contexts that span metric and imperial systems.
1 ftm × 0.0909090909 = 0.0909090909 ch
Fathom to Chain conversion table
Standard reference values for converting fathoms to chains:
| Fathom [ftm] | Chain [ch] |
|---|---|
| 0.01 | 0.0009090909 |
| 0.1 | 0.0090909091 |
| 1 | 0.0909090909 |
| 2 | 0.1818181818 |
| 3 | 0.2727272727 |
| 4 | 0.3636363636 |
| 5 | 0.4545454545 |
| 10 | 0.9090909091 |
| 20 | 1.8181818182 |
| 30 | 2.7272727273 |
| 40 | 3.6363636364 |
| 50 | 4.5454545455 |
| 100 | 9.0909090909 |
| 500 | 45.4545454545 |
| 1000 | 90.9090909091 |
Frequently asked questions
How many chains is 1 fathom?
How do I convert fathoms to chains?
How do I convert chains back to fathoms?
How many chains is 100 fathoms?
Popular length unit conversions
Convert Fathom to other length units
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Metric / SI (7 units)
Imperial / US Customary (26 units)
Nautical (1 units)
Sources & references
Conversion factor (1 ftm = 0.0909090909 ch) verified against the following authoritative sources:
- BIPM — The International System of Units (SI Brochure 9th ed.)
Official BIPM publication defining the seven SI base units (including the meter) and the rules for their use. The global authority on units of measurement.
- NIST — Guide to the SI
US National Institute of Standards and Technology reference covering the SI base and derived units with definitions and usage rules for US technical practice.
- NIST Special Publication 811 — Guide for the Use of the International System of Units
Detailed NIST guide covering exact conversion factors between SI and US customary units along with formatting and rounding conventions.
- NIST — Refinement of values for the yard and pound (Federal Register 1959)
The treaty (signed by US
- International Astronomical Union — System of Astronomical Constants
The IAU defines astronomical units including the AU (149597870700 m exactly) light-year and parsec used in astronomy and astrophysics.