Convert X-unit to Bohr Radius
Convert x-units to bohr radii instantly. 1 x-unit = 0.0018936945 bohr radius — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Bohr Radius 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Defined by Manne Siegbahn in 1925; superseded by direct SI measurement of X-ray wavelengths after the 1960s; retained in literature for historical comparison.
Bohr Radius
The Bohr radius is approximately 5.292×10⁻¹¹ meters — the most probable distance between the proton and electron in a hydrogen atom in its ground state.
Defined by Niels Bohr in his 1913 model of the hydrogen atom. The current CODATA 2018 value of 5.29177210903×10⁻¹¹ m is derived from the elementary charge, electron mass, and Planck's constant.
The Bohr radius is used throughout atomic physics, quantum chemistry, and computational chemistry as the natural length scale for electronic-structure calculations. The atomic unit (a.u.) of length equals the Bohr radius.
Defined by Bohr in 1913; current value via CODATA 2018.
X-unit to Bohr Radius conversion formula
The relationship between x-units and bohr radii:
To convert x-units to bohr radii, multiply the value in x-units by 0.0018936945. To reverse, multiply bohr radii by 528.0682675412.
How to use this converter
Type a value into the calculator. The result in bohr radii updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Bohr Radius to X-unit converter for the reverse direction.
Step-by-step: convert x-units to bohr radii
- Write down the value in x-units (X).
- Multiply that value by the factor 0.0018936945.
- The product is the equivalent value in bohr radii (a₀).
- To reverse, multiply the bohr radius value by 528.0682675412.
Worked examples
Example 1 — Convert 1 X to a₀:
1 × 0.0018936945 = 0.0018936945 a₀
Example 2 — Convert 100 X to a₀:
100 × 0.0018936945 = 0.1893694549 a₀
Real-world example — Wavelengths across the spectrum
Optical and atomic-scale phenomena are routinely cross-converted between sub-micron units. A photon of wavelength 800 x-units can be re-expressed in bohr radii for direct comparison with another instrument's calibration data sheet.
800 X × 0.0018936945 = 1.5149556396 a₀
Real-world example — Molecular dimensions
The diameter of small molecular structures (around 2 x-units) is often converted into related sub-micron units when comparing measurements across different microscopy techniques or imaging modalities.
2 X × 0.0018936945 = 0.0037873891 a₀
X-unit to Bohr Radius conversion table
Standard reference values for converting x-units to bohr radii:
| X-unit [X] | Bohr Radius [a₀] |
|---|---|
| 0.01 | 1.893695e-5 |
| 0.1 | 0.0001893695 |
| 1 | 0.0018936945 |
| 2 | 0.0037873891 |
| 3 | 0.0056810836 |
| 4 | 0.0075747782 |
| 5 | 0.0094684727 |
| 10 | 0.0189369455 |
| 20 | 0.037873891 |
| 30 | 0.0568108365 |
| 40 | 0.075747782 |
| 50 | 0.0946847275 |
| 100 | 0.1893694549 |
| 500 | 0.9468472747 |
| 1000 | 1.8936945495 |
Frequently asked questions
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Imperial / US Customary (4 units)
Sources & references
Conversion factor (1 X = 0.0018936945 a₀) 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.