Convert Microinch to Inch
Convert microinches to inches instantly. 1 microinch = 1e-6 inch — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Inch 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.
Inch
An inch is an Imperial and US customary unit of length defined since 1959 as exactly 25.4 millimeters (0.0254 meters). It is still the standard small unit of length in the United States, the United Kingdom (informally), and a few other countries.
The inch derives from the Roman uncia (one-twelfth of a foot) and survived through Anglo-Saxon and medieval English measurement systems. Various definitions persisted regionally until the 1959 International Yard and Pound Agreement standardized the inch globally as exactly 25.4 mm.
Inches are used in the US and UK for body height, screen sizes (TVs, monitors, phones), tire sizes, plumbing, lumber, paper sizes (US Letter is 8.5 × 11 in), and most consumer product specifications in the United States.
Anglo-Saxon origin (predating 1066); standardized to 25.4 mm exactly by the International Yard and Pound Agreement of 1959, signed by the US, UK, Canada, Australia, New Zealand, and South Africa.
Microinch to Inch conversion formula
The relationship between microinches and inches:
To convert microinches to inches, multiply the value in microinches by 1e-6. To reverse, multiply inches by 1000000.
How to use this converter
Type a value into the calculator. The result in inches updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Inch to Microinch converter for the reverse direction.
Step-by-step: convert microinches to inches
- Write down the value in microinches (µin).
- Multiply that value by the factor 1e-6.
- The product is the equivalent value in inches (in).
- To reverse, multiply the inch value by 1000000.
Worked examples
Example 1 — Convert 1 µin to in:
1 × 1e-6 = 1e-6 in
Example 2 — Convert 100 µin to in:
100 × 1e-6 = 1e-4 in
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 inches — useful when relating optical-wavelength specifications to physical mounting hardware.
1000000 µin × 1e-6 = 1 in
Real-world example — Sub-micron to millimeter
500,000 microinches converts to a small everyday quantity in inches — useful when relating optical-wavelength specifications to physical mounting hardware.
500000 µin × 1e-6 = 0.5 in
Microinch to Inch conversion table
Standard reference values for converting microinches to inches:
| Microinch [µin] | Inch [in] |
|---|---|
| 0.01 | 1e-8 |
| 0.1 | 1e-7 |
| 1 | 1e-6 |
| 2 | 2e-6 |
| 3 | 3e-6 |
| 4 | 4e-6 |
| 5 | 5e-6 |
| 10 | 1e-5 |
| 20 | 2e-5 |
| 30 | 3e-5 |
| 40 | 4e-5 |
| 50 | 5e-5 |
| 100 | 1e-4 |
| 500 | 0.0005 |
| 1000 | 0.001 |
Frequently asked questions
How many inches is 1 microinch?
How do I convert microinches to inches?
How do I convert inches back to microinches?
How many inches is 100 microinches?
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Metric / SI (4 units)
Imperial / US Customary (26 units)
Sources & references
Conversion factor (1 µin = 1e-6 in) 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.