Convert Microinch to Barleycorn
Convert microinches to barleycorns instantly. 1 microinch = 3e-6 barleycorn — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Barleycorn to Microinch converter for the reverse conversion.
Units explained
Microinch
A microinch is an Imperial unit of length equal to one millionth of an inch (2.54×10⁻⁸ m). It is used almost exclusively in surface-finish specifications for precision machining and optical components.
The microinch is derived from the inch using the SI-style prefix micro- to denote one millionth. Standardised through the 1959 International Yard and Pound Agreement, which fixed the inch at exactly 25.4 mm.
Microinches express surface roughness (Ra values) in US-based precision manufacturing — typical machined surfaces are 16–125 µin. Optical components and bearing races are often specified to 1–4 µin Ra.
Used in US precision-manufacturing literature throughout the 20th century; value became exact in 1959 when the inch was fixed at 25.4 mm via the International Yard and Pound Agreement.
Barleycorn
A barleycorn is an Imperial unit of length equal to one third of an inch (about 8.47 mm). It is the basis of UK shoe sizing and is one of the oldest English length units still in use.
The barleycorn derives from the average length of a grain of barley as a natural reference. Standardised at exactly 1/3 inch by the Statute of Edward II in 1324, which used three barleycorns to define an inch.
Barleycorns are the foundation of UK and US children's shoe sizing — each whole size differs by one barleycorn. Also occasionally referenced in horse-handling and historical English literature.
Standardised in 1324 by the Statute of Edward II at 1/3 inch; the value became exact in 1959 when the inch was fixed at 25.4 mm.
Microinch to Barleycorn conversion formula
The relationship between microinches and barleycorns:
To convert microinches to barleycorns, multiply the value in microinches by 3e-6. To reverse, multiply barleycorns by 333333.3346456693.
How to use this converter
Type a value into the calculator. The result in barleycorns updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Barleycorn to Microinch converter for the reverse direction.
Step-by-step: convert microinches to barleycorns
- Write down the value in microinches (µin).
- Multiply that value by the factor 3e-6.
- The product is the equivalent value in barleycorns (barleycorn).
- To reverse, multiply the barleycorn value by 333333.3346456693.
Worked examples
Example 1 — Convert 1 µin to barleycorn:
1 × 3e-6 = 3e-6 barleycorn
Example 2 — Convert 100 µin to barleycorn:
100 × 3e-6 = 0.0003 barleycorn
Real-world example — Sub-micron to millimeter
500,000 microinches converts to a small everyday quantity in barleycorns — useful when relating optical-wavelength specifications to physical mounting hardware.
500000 µin × 3e-6 = 1.4999999941 barleycorn
Real-world example — From wavelengths to millimeter-scale objects
A value of one million microinches sounds vast at the atomic scale but converts to a small everyday quantity in barleycorns — useful when relating optical-wavelength specifications to physical mounting hardware.
1000000 µin × 3e-6 = 2.9999999882 barleycorn
Microinch to Barleycorn conversion table
Standard reference values for converting microinches to barleycorns:
| Microinch [µin] | Barleycorn [barleycorn] |
|---|---|
| 0.01 | 3e-8 |
| 0.1 | 3e-7 |
| 1 | 3e-6 |
| 2 | 6e-6 |
| 3 | 9e-6 |
| 4 | 1.2e-5 |
| 5 | 1.5e-5 |
| 10 | 3e-5 |
| 20 | 6e-5 |
| 30 | 9e-5 |
| 40 | 0.00012 |
| 50 | 0.00015 |
| 100 | 0.0003 |
| 500 | 0.0015 |
| 1000 | 0.003 |
Frequently asked questions
How many barleycorns is 1 microinch?
How do I convert microinches to barleycorns?
How do I convert barleycorns back to microinches?
How many barleycorns is 100 microinches?
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Metric / SI (4 units)
Imperial / US Customary (26 units)
Sources & references
Conversion factor (1 µin = 3e-6 barleycorn) 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.