Convert Barleycorn to Millimeter
Convert barleycorns to millimeters instantly. 1 barleycorn = 8.4666667 millimeter — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Millimeter 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.
Millimeter
A millimeter is a metric unit of length equal to one thousandth of a meter (1/1000 m). It is the standard small-scale unit in the SI system and is widely used wherever sub-centimeter precision matters.
The millimeter was defined alongside the meter when France adopted the metric system in 1795, using the standard SI prefix milli- (from Latin mille, "thousand") to denote one-thousandth.
Millimeters are used in engineering drawings, machining, manufacturing, paper sizes, rainfall measurement, and any context where dimensions below one centimeter need to be specified clearly. Most rulers worldwide are marked in millimeters.
Adopted in 1795 in France as part of the original metric system; standardized internationally by the Metre Convention in 1875 and confirmed in the SI in 1960.
Barleycorn to Millimeter conversion formula
The relationship between barleycorns and millimeters:
To convert barleycorns to millimeters, multiply the value in barleycorns by 8.4666667. To reverse, multiply millimeters by 0.1181102358.
How to use this converter
Type a value into the calculator. The result in millimeters updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Millimeter to Barleycorn converter for the reverse direction.
Step-by-step: convert barleycorns to millimeters
- Write down the value in barleycorns (barleycorn).
- Multiply that value by the factor 8.4666667.
- The product is the equivalent value in millimeters (mm).
- To reverse, multiply the millimeter value by 0.1181102358.
Worked examples
Example 1 — Convert 1 barleycorn to mm:
1 × 8.4666667 = 8.4666667 mm
Example 2 — Convert 100 barleycorn to mm:
100 × 8.4666667 = 846.66667 mm
Real-world example — Postcard and small-object dimensions
A postcard is about 5 barleycorns wide. Converting to millimeters is essential for international postal addressing forms that ask for dimensions in different units across countries.
5 barleycorn × 8.4666667 = 42.3333335 mm
Real-world example — Ruler-scale measurements
A 30-barleycorn school ruler converts cleanly to millimeters — useful when buying a desk accessory from a retailer whose product specs use a different unit.
30 barleycorn × 8.4666667 = 254.000001 mm
Real-world example — Hardware-scale dimensions
A 10-barleycorn fastener or component is about as long as a thumbnail. Mechanics and DIY enthusiasts convert between barleycorns and millimeters daily when mixing metric and imperial tools.
10 barleycorn × 8.4666667 = 84.666667 mm
Barleycorn to Millimeter conversion table
Standard reference values for converting barleycorns to millimeters:
| Barleycorn [barleycorn] | Millimeter [mm] |
|---|---|
| 0.01 | 0.084666667 |
| 0.1 | 0.84666667 |
| 1 | 8.4666667 |
| 2 | 16.9333334 |
| 3 | 25.4000001 |
| 4 | 33.8666668 |
| 5 | 42.3333335 |
| 10 | 84.666667 |
| 20 | 169.333334 |
| 30 | 254.000001 |
| 40 | 338.666668 |
| 50 | 423.333335 |
| 100 | 846.66667 |
| 500 | 4233.33335 |
| 1000 | 8466.6667 |
Frequently asked questions
How many millimeters is 1 barleycorn?
How do I convert barleycorns to millimeters?
How do I convert millimeters back to barleycorns?
How many millimeters 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 = 8.4666667 mm) 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.