Convert US Survey Foot to Fathom
Convert us survey feet to fathoms instantly. 1 us survey foot = 0.166667 fathom — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Fathom to US Survey Foot converter for the reverse conversion.
Units explained
US Survey Foot
The US Survey Foot is a legacy unit of length defined as exactly 1200/3937 meters (approximately 0.3048006 m). It differs from the modern international foot by about 2 parts per million.
Established in the United States by the Mendenhall Order of 1893, which defined the foot in terms of the meter as 1200/3937 m. The US continued using this value for surveying even after the 1959 International Yard and Pound Agreement standardized the international foot at exactly 0.3048 m.
Used in US land surveying, geodetic measurements, state plane coordinate systems, and legal land descriptions. The US Survey Foot was officially deprecated by NIST and NOAA effective December 31, 2022, with the international foot becoming the sole US standard. Legacy data and recorded land surveys still reference it.
Mendenhall Order of 1893 defined the foot as 1200/3937 m; persisted in US surveying after 1959; officially deprecated by NIST/NOAA as of December 31, 2022.
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.
US Survey Foot to Fathom conversion formula
Note: this conversion uses a generally accepted modern value. Historical and regional definitions of this unit varied across times and places.
The relationship between us survey feet and fathoms:
To convert us survey feet to fathoms, multiply the value in us survey feet by 0.166667. To reverse, multiply fathoms by 5.999988.
How to use this converter
Type a value into the calculator. The result in fathoms updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Fathom to US Survey Foot converter for the reverse direction.
Step-by-step: convert us survey feet to fathoms
- Write down the value in us survey feet (sft).
- Multiply that value by the factor 0.166667.
- The product is the equivalent value in fathoms (ftm).
- To reverse, multiply the fathom value by 5.999988.
Worked examples
Example 1 — Convert 1 sft to ftm:
1 × 0.166667 = 0.166667 ftm
Example 2 — Convert 100 sft to ftm:
100 × 0.166667 = 16.6667000001 ftm
Real-world example — Maritime depth conversion
A 10-us survey foot sounding depth converts cleanly into fathoms. Recreational divers and sailors translate between the two units whenever they read legacy charts against modern depth-sounder displays.
10 sft × 0.166667 = 1.66667 ftm
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 sft × 0.166667 = 0.166667 ftm
Real-world example — Adult height conversion
A 1.8-us survey foot-tall person measures a value in fathoms that converts the height to the unit favoured by American forms, schools, or driver's licences. This is daily routine for anyone living between metric and imperial systems.
1.8 sft × 0.166667 = 0.3000006 ftm
US Survey Foot to Fathom conversion table
Standard reference values for converting us survey feet to fathoms:
| US Survey Foot [sft] | Fathom [ftm] |
|---|---|
| 0.01 | 0.00166667 |
| 0.1 | 0.0166667 |
| 1 | 0.166667 |
| 2 | 0.333334 |
| 3 | 0.500001 |
| 4 | 0.666668 |
| 5 | 0.833335 |
| 10 | 1.66667 |
| 20 | 3.33334 |
| 30 | 5.00001 |
| 40 | 6.66668 |
| 50 | 8.33335 |
| 100 | 16.6667000001 |
| 500 | 83.3335000003 |
| 1000 | 166.6670000007 |
Frequently asked questions
How many fathoms is 1 us survey foot?
How do I convert us survey feet to fathoms?
How do I convert fathoms back to us survey feet?
How many fathoms is 100 us survey feet?
Popular length unit conversions
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Metric / SI (7 units)
Imperial / US Customary (26 units)
Nautical (1 units)
Sources & references
Conversion factor (1 sft = 0.166667 ftm) 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 Hydrographic Organization — Resolution on the Nautical Mile
International authority that standardised the nautical mile at exactly 1852 m in 1929 — the value adopted worldwide for sea and air navigation.