Convert X-unit to Foot
Convert x-units to feet instantly. 1 x-unit = 3.28773e-13 foot — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Foot to X-unit converter for the reverse conversion.
Units explained
X-unit
The X-unit (or siegbahn) is a historical X-ray crystallography unit of approximately 1.0021×10⁻¹³ meters. It was used before X-ray wavelengths could be measured directly in meters.
Introduced by Manne Siegbahn in 1925 as a self-consistent unit for X-ray crystallography. The 'X-unit' was defined to make the X-ray wavelength of the molybdenum K-alpha line a round number.
X-units appear in X-ray crystallography literature from 1925 through the 1960s. Modern crystallography uses meters or angstroms; X-units are mostly of historical interest now.
Defined by Manne Siegbahn in 1925; superseded by direct SI measurement of X-ray wavelengths after the 1960s; retained in literature for historical comparison.
Foot
A foot is an Imperial and US customary unit of length equal to 12 inches or exactly 0.3048 meters. It is the most commonly used unit of length in everyday measurement in the United States.
The foot's origin is literally the length of a human foot, used as a measurement standard since antiquity. The English foot was standardized at various points in history; the modern international foot (0.3048 m exactly) was fixed by the 1959 International Yard and Pound Agreement.
Feet are used in the US for body height, building dimensions, room sizes, road sign clearances, aviation altitude (feet above sea level), and most everyday distance estimation. The UK uses feet informally for height despite officially being metric.
Used since antiquity; standardized to 0.3048 m exactly by the International Yard and Pound Agreement of 1959. Aviation worldwide uses feet for altitude despite metric adoption elsewhere.
X-unit to Foot conversion formula
The relationship between x-units and feet:
To convert x-units to feet, multiply the value in x-units by 3.28773e-13. To reverse, multiply feet by 3.041613e+12.
How to use this converter
Type a value into the calculator. The result in 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 Foot to X-unit converter for the reverse direction.
Step-by-step: convert x-units to feet
- Write down the value in x-units (X).
- Multiply that value by the factor 3.28773e-13.
- The product is the equivalent value in feet (ft).
- To reverse, multiply the foot value by 3.041613e+12.
Worked examples
Example 1 — Convert 1 X to ft:
1 × 3.28773e-13 = 3.28773e-13 ft
Example 2 — Convert 100 X to ft:
100 × 3.28773e-13 = 3.28773e-11 ft
Real-world example — Bridging nine orders of magnitude
500 million x-units equals a value comfortably in the human-scale feet range. Physics problems that span this gap are common when comparing the wavelength of light to the path length of an experiment.
5e+8 X × 3.28773e-13 = 0.0001643865 ft
Real-world example — From sub-micron to human scale
One billion x-units equals one foot — the conversion that drives home the gulf between atomic-scale features and everyday objects in physics curricula.
1e+9 X × 3.28773e-13 = 0.000328773 ft
X-unit to Foot conversion table
Standard reference values for converting x-units to feet:
| X-unit [X] | Foot [ft] |
|---|---|
| 0.01 | 3.28773e-15 |
| 0.1 | 3.28773e-14 |
| 1 | 3.28773e-13 |
| 2 | 6.575459e-13 |
| 3 | 9.863189e-13 |
| 4 | 1.315092e-12 |
| 5 | 1.643865e-12 |
| 10 | 3.28773e-12 |
| 20 | 6.575459e-12 |
| 30 | 9.863189e-12 |
| 40 | 1.315092e-11 |
| 50 | 1.643865e-11 |
| 100 | 3.28773e-11 |
| 500 | 1.643865e-10 |
| 1000 | 3.28773e-10 |
Frequently asked questions
How many feet is 1 x-unit?
How do I convert x-units to feet?
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How many feet is 100 x-units?
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Metric / SI (4 units)
Imperial / US Customary (4 units)
Sources & references
Conversion factor (1 X = 3.28773e-13 ft) 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.