Convert Span to Fathom
Convert spans to fathoms instantly. 1 span = 0.125 fathom — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Fathom to Span converter for the reverse conversion.
Units explained
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
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 to Fathom conversion formula
The relationship between spans and fathoms:
To convert spans to fathoms, multiply the value in spans by 0.125. To reverse, multiply fathoms by 8.
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 Span converter for the reverse direction.
Step-by-step: convert spans to fathoms
- Write down the value in spans (span).
- Multiply that value by the factor 0.125.
- The product is the equivalent value in fathoms (ftm).
- To reverse, multiply the fathom value by 8.
Worked examples
Example 1 — Convert 1 span to ftm:
1 × 0.125 = 0.125 ftm
Example 2 — Convert 100 span to ftm:
100 × 0.125 = 12.5 ftm
Real-world example — Adult height conversion
A 1.8-span-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 span × 0.125 = 0.225 ftm
Real-world example — Fabric purchase length
Two spans of fabric equals a value in fathoms essential for tailors and textile buyers sourcing material from international suppliers that quote in different units.
2 span × 0.125 = 0.25 ftm
Real-world example — Maritime depth conversion
A 10-span 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 span × 0.125 = 1.25 ftm
Span to Fathom conversion table
Standard reference values for converting spans to fathoms:
| Span [span] | Fathom [ftm] |
|---|---|
| 0.01 | 0.00125 |
| 0.1 | 0.0125 |
| 1 | 0.125 |
| 2 | 0.25 |
| 3 | 0.375 |
| 4 | 0.5 |
| 5 | 0.625 |
| 10 | 1.25 |
| 20 | 2.5 |
| 30 | 3.75 |
| 40 | 5 |
| 50 | 6.25 |
| 100 | 12.5 |
| 500 | 62.5 |
| 1000 | 125 |
Frequently asked questions
How many fathoms is 1 span?
How do I convert spans to fathoms?
How do I convert fathoms back to spans?
How many fathoms is 100 spans?
Popular length unit conversions
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Metric / SI (4 units)
Imperial / US Customary (26 units)
Sources & references
Conversion factor (1 span = 0.125 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.