Convert Hand to Microinch
Convert hands to microinches instantly. 1 hand = 4000000 microinch — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Microinch to Hand converter for the reverse conversion.
Units explained
Hand
A hand is an Imperial unit of length equal to 4 inches (101.6 mm). It is used primarily to measure the height of horses at the withers.
The hand derives from the average breadth of a human hand and was standardised at exactly 4 inches by the Statute of Henry VIII in 1541.
Hands are used worldwide for horse height specification (the typical riding horse is 14–17 hh). Also used in some equestrian-adjacent contexts. The unit is now almost exclusively a horse-measurement convention.
Standardised at 4 inches by Henry VIII in 1541; 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.
Hand to Microinch conversion formula
The relationship between hands and microinches:
To convert hands to microinches, multiply the value in hands by 4000000. To reverse, multiply microinches by 2.5e-7.
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 Hand converter for the reverse direction.
Step-by-step: convert hands to microinches
- Write down the value in hands (hh).
- Multiply that value by the factor 4000000.
- The product is the equivalent value in microinches (µin).
- To reverse, multiply the microinch value by 2.5e-7.
Worked examples
Example 1 — Convert 1 hh to µin:
1 × 4000000 = 4000000 µin
Example 2 — Convert 100 hh to µin:
100 × 4000000 = 4e+8 µin
Real-world example — Human-scale to atomic dimensions
One hand equals one billion microinches — the canonical metric conversion bridging everyday objects and atomic-scale features in physics, chemistry, and electronics.
1 hh × 4000000 = 4000000 µin
Real-world example — Meter to nanoscale
One hand equals one billion microinches. Physics curricula use this conversion to teach orders of magnitude when introducing the electromagnetic spectrum.
1 hh × 4000000 = 4000000 µin
Hand to Microinch conversion table
Standard reference values for converting hands to microinches:
| Hand [hh] | Microinch [µin] |
|---|---|
| 0.01 | 40000 |
| 0.1 | 400000 |
| 1 | 4000000 |
| 2 | 8000000 |
| 3 | 1.2e+7 |
| 4 | 1.6e+7 |
| 5 | 2e+7 |
| 10 | 4e+7 |
| 20 | 8e+7 |
| 30 | 1.2e+8 |
| 40 | 1.6e+8 |
| 50 | 2e+8 |
| 100 | 4e+8 |
| 500 | 2e+9 |
| 1000 | 4e+9 |
Frequently asked questions
How many microinches is 1 hand?
How do I convert hands to microinches?
How do I convert microinches back to hands?
How many microinches is 100 hands?
Popular length unit conversions
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Metric / SI (4 units)
Imperial / US Customary (26 units)
Sources & references
Conversion factor (1 hh = 4000000 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.