How the conversion works
Most modern nautical and diving references assume 1 fathom = 6 feet. This comes from the idea of a “fathom” being the span of outstretched arms.
Historically, there were small variations — for example the Admiralty fathom of 6.08 ft. That’s why this page gives you multiple presets.
Formulas
feet = fathoms × fathom_length
Standard: feet = fathoms × 6
Admiralty: feet = fathoms × 6.08
fathoms = feet ÷ fathom_length
Example: 48 ft ÷ 6 = 8 fathoms
FAQ
1. Which fathom should I use?
If your chart or document doesn’t say otherwise, use 6 ft. If you are checking older British naval material, try 6.08 ft.
2. How do I go to meters?
First convert to feet, then multiply by 0.3048. Example: 5 fathoms × 6 ft/fathom = 30 ft. 30 ft × 0.3048 = 9.144 m.
3. Why are there different fathoms?
Because different navies and periods standardized slightly different lengths. Today, 6 ft is the simplest and most common.
Formula (LaTeX) + variables + units
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feet = fathoms × fathom_length Standard: feet = fathoms × 6 Admiralty: feet = fathoms × 6.08
fathoms = feet ÷ fathom_length Example: 48 ft ÷ 6 = 8 fathoms
- No variables provided in audit spec.
- NIST — Weights and measures — nist.gov · Accessed 2026-01-19
https://www.nist.gov/pml/weights-and-measures - NIST — SI units — nist.gov · Accessed 2026-01-19
https://www.nist.gov/pml/owm/metric-si/si-units
Last code update: 2026-01-19
- Initial audit spec draft generated from HTML extraction (review required).
- Verify formulas match the calculator engine and convert any text-only formulas to LaTeX.
- Confirm sources are authoritative and relevant to the calculator methodology.