Convert Barleycorn to Microinch
Convert barleycorns to microinches instantly. 1 barleycorn = 333333.3346456693 microinch — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Microinch to Barleycorn converter for the reverse conversion.
Units explained
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
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 to Microinch conversion formula
The relationship between barleycorns and microinches:
To convert barleycorns to microinches, multiply the value in barleycorns by 333333.3346456693. To reverse, multiply microinches by 3e-6.
How to use this converter
Type a value into the calculator. The result in microinches updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Microinch to Barleycorn converter for the reverse direction.
Step-by-step: convert barleycorns to microinches
- Write down the value in barleycorns (barleycorn).
- Multiply that value by the factor 333333.3346456693.
- The product is the equivalent value in microinches (µin).
- To reverse, multiply the microinch value by 3e-6.
Worked examples
Example 1 — Convert 1 barleycorn to µin:
1 × 333333.3346456693 = 333333.3346456693 µin
Example 2 — Convert 100 barleycorn to µin:
100 × 333333.3346456693 = 3.333333e+7 µin
Real-world example — Small-scale to atomic-scale
One barleycorn equals 10 million microinches — useful for physics curricula that relate everyday measurements to atomic and optical scales.
1 barleycorn × 333333.3346456693 = 333333.3346456693 µin
Real-world example — Centimeter to wavelength scale
One barleycorn equals 10 million microinches. Physics curricula use this kind of conversion to relate everyday measurements to atomic and optical scales.
1 barleycorn × 333333.3346456693 = 333333.3346456693 µin
Barleycorn to Microinch conversion table
Standard reference values for converting barleycorns to microinches:
| Barleycorn [barleycorn] | Microinch [µin] |
|---|---|
| 0.01 | 3333.3333464567 |
| 0.1 | 33333.3334645669 |
| 1 | 333333.3346456693 |
| 2 | 666666.6692913387 |
| 3 | 1000000.003937008 |
| 4 | 1333333.3385826773 |
| 5 | 1666666.6732283467 |
| 10 | 3333333.3464566935 |
| 20 | 6666666.692913387 |
| 30 | 1e+7 |
| 40 | 1.333333e+7 |
| 50 | 1.666667e+7 |
| 100 | 3.333333e+7 |
| 500 | 1.666667e+8 |
| 1000 | 3.333333e+8 |
Frequently asked questions
How many microinches is 1 barleycorn?
How do I convert barleycorns to microinches?
How do I convert microinches back to barleycorns?
How many microinches is 100 barleycorns?
Popular length unit conversions
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Metric / SI (4 units)
Imperial / US Customary (26 units)
Sources & references
Conversion factor (1 barleycorn = 333333.3346456693 µin) 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.