Convert Fathom to Span
Convert fathoms to spans instantly. 1 fathom = 8 span — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Span 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.
Span
A span is an Imperial unit of length equal to 9 inches (228.6 mm). Historically, it represented the distance from the tip of an extended thumb to the tip of an extended little finger.
The span derives from this natural body-measurement and was standardised at 9 inches in English customary practice.
Spans are rare in modern commerce but appear in historical English literature, biblical translation studies, and reproduction crafts. Some construction and gardening still use 'span' informally.
Ancient body-measure origin; standardised in English customary practice at 9 inches; became exact via the 1959 International Yard and Pound Agreement.
Fathom to Span conversion formula
The relationship between fathoms and spans:
To convert fathoms to spans, multiply the value in fathoms by 8. To reverse, multiply spans by 0.125.
How to use this converter
Type a value into the calculator. The result in spans updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Span to Fathom converter for the reverse direction.
Step-by-step: convert fathoms to spans
- Write down the value in fathoms (ftm).
- Multiply that value by the factor 8.
- The product is the equivalent value in spans (span).
- To reverse, multiply the span value by 0.125.
Worked examples
Example 1 — Convert 1 ftm to span:
1 × 8 = 8 span
Example 2 — Convert 100 ftm to span:
100 × 8 = 800 span
Real-world example — Maritime depth conversion
A 10-fathom sounding depth converts cleanly into spans. Recreational divers and sailors translate between the two units whenever they read legacy charts against modern depth-sounder displays.
10 ftm × 8 = 80 span
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 × 8 = 8 span
Real-world example — Adult height conversion
A 1.8-fathom-tall person measures a value in spans 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 ftm × 8 = 14.4 span
Fathom to Span conversion table
Standard reference values for converting fathoms to spans:
| Fathom [ftm] | Span [span] |
|---|---|
| 0.01 | 0.08 |
| 0.1 | 0.8 |
| 1 | 8 |
| 2 | 16 |
| 3 | 24 |
| 4 | 32 |
| 5 | 40 |
| 10 | 80 |
| 20 | 160 |
| 30 | 240 |
| 40 | 320 |
| 50 | 400 |
| 100 | 800 |
| 500 | 4000 |
| 1000 | 8000 |
Frequently asked questions
How many spans is 1 fathom?
How do I convert fathoms to spans?
How do I convert spans back to fathoms?
How many spans is 100 fathoms?
Popular length unit conversions
Convert Fathom to other length units
Show all Fathom conversions
Metric / SI (7 units)
Imperial / US Customary (26 units)
Nautical (1 units)
Sources & references
Conversion factor (1 ftm = 8 span) 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.