Convert US Survey Foot to Span
Convert us survey feet to spans instantly. 1 us survey foot = 1.333336 span — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Span 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.
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 to Span 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 spans:
To convert us survey feet to spans, multiply the value in us survey feet by 1.333336. To reverse, multiply spans by 0.7499985.
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 US Survey Foot converter for the reverse direction.
Step-by-step: convert us survey feet to spans
- Write down the value in us survey feet (sft).
- Multiply that value by the factor 1.333336.
- The product is the equivalent value in spans (span).
- To reverse, multiply the span value by 0.7499985.
Worked examples
Example 1 — Convert 1 sft to span:
1 × 1.333336 = 1.333336 span
Example 2 — Convert 100 sft to span:
100 × 1.333336 = 133.3336000005 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 sft × 1.333336 = 1.333336 span
Real-world example — Adult height conversion
A 1.8-us survey foot-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 sft × 1.333336 = 2.4000048 span
Real-world example — Fabric purchase length
Two us survey feet of fabric equals a value in spans essential for tailors and textile buyers sourcing material from international suppliers that quote in different units.
2 sft × 1.333336 = 2.666672 span
US Survey Foot to Span conversion table
Standard reference values for converting us survey feet to spans:
| US Survey Foot [sft] | Span [span] |
|---|---|
| 0.01 | 0.01333336 |
| 0.1 | 0.1333336 |
| 1 | 1.333336 |
| 2 | 2.666672 |
| 3 | 4.000008 |
| 4 | 5.333344 |
| 5 | 6.66668 |
| 10 | 13.3333600001 |
| 20 | 26.6667200001 |
| 30 | 40.0000800002 |
| 40 | 53.3334400002 |
| 50 | 66.6668000003 |
| 100 | 133.3336000005 |
| 500 | 666.6680000027 |
| 1000 | 1333.3360000053 |
Frequently asked questions
How many spans is 1 us survey foot?
How do I convert us survey feet to spans?
How do I convert spans back to us survey feet?
How many spans is 100 us survey feet?
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Metric / SI (7 units)
Imperial / US Customary (26 units)
Nautical (1 units)
Sources & references
Conversion factor (1 sft = 1.333336 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 Astronomical Union — System of Astronomical Constants
The IAU defines astronomical units including the AU (149597870700 m exactly) light-year and parsec used in astronomy and astrophysics.