Convert Span to US Survey Foot
Convert spans to us survey feet instantly. 1 span = 0.7499985 us survey foot — use the live calculator, the exact formula, a conversion table and worked examples. Also check the US Survey Foot 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.
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.
Span to US Survey Foot 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 spans and us survey feet:
To convert spans to us survey feet, multiply the value in spans by 0.7499985. To reverse, multiply us survey feet by 1.333336.
How to use this converter
Type a value into the calculator. The result in us survey feet updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the US Survey Foot to Span converter for the reverse direction.
Step-by-step: convert spans to us survey feet
- Write down the value in spans (span).
- Multiply that value by the factor 0.7499985.
- The product is the equivalent value in us survey feet (sft).
- To reverse, multiply the us survey foot value by 1.333336.
Worked examples
Example 1 — Convert 1 span to sft:
1 × 0.7499985 = 0.7499985 sft
Example 2 — Convert 100 span to sft:
100 × 0.7499985 = 74.99985 sft
Real-world example — Adult height conversion
A 1.8-span-tall person measures a value in us survey feet 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 × 0.7499985 = 1.3499973 sft
Real-world example — Fabric purchase length
Two spans of fabric equals a value in us survey feet essential for tailors and textile buyers sourcing material from international suppliers that quote in different units.
2 span × 0.7499985 = 1.499997 sft
Real-world example — Maritime depth conversion
A 10-span sounding depth converts cleanly into us survey feet. Recreational divers and sailors translate between the two units whenever they read legacy charts against modern depth-sounder displays.
10 span × 0.7499985 = 7.499985 sft
Span to US Survey Foot conversion table
Standard reference values for converting spans to us survey feet:
| Span [span] | US Survey Foot [sft] |
|---|---|
| 0.01 | 0.007499985 |
| 0.1 | 0.07499985 |
| 1 | 0.7499985 |
| 2 | 1.499997 |
| 3 | 2.2499955 |
| 4 | 2.999994 |
| 5 | 3.7499925 |
| 10 | 7.499985 |
| 20 | 14.99997 |
| 30 | 22.499955 |
| 40 | 29.99994 |
| 50 | 37.499925 |
| 100 | 74.99985 |
| 500 | 374.99925 |
| 1000 | 749.9985 |
Frequently asked questions
How many us survey feet is 1 span?
How do I convert spans to us survey feet?
How do I convert us survey feet back to spans?
How many us survey feet is 100 spans?
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Sources & references
Conversion factor (1 span = 0.7499985 sft) 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.