Convert Square Mil to Square Thou
Convert square mils to square thous instantly. 1 square mil = 1 square thou — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Square Thou to Square Mil converter for the reverse conversion.
Units explained
Square Mil
A square mil is an imperial unit of area equal to 6.4516×10⁻¹⁰ m². It is widely used in printed circuit board (PCB) design and electronics manufacturing.
Derived by squaring the mil (1 mil = 1/1000 of an inch = 0.0254 mm). Standardized via the 1959 International Yard and Pound Agreement.
Square mils are the standard unit for PCB trace cross-sections, pad areas, and component pitches in US-localized electronic design software and datasheets.
Standardized via the 1959 International Yard and Pound Agreement.
Square Thou
A square thou is an imperial unit of area equal to 6.4516×10⁻¹⁰ m², identical to the square mil. The word 'thou' is short for 'thousandth' (of an inch).
Identical in value to the square mil; 'thou' is the British engineering term, 'mil' is the American term. Both refer to 1/1000 of an inch.
Square thous are used in British and Commonwealth engineering contexts where 'thou' is preferred over 'mil', particularly in mechanical engineering tolerance specifications.
Standardized via the 1959 International Yard and Pound Agreement.
Square Mil to Square Thou conversion formula
The relationship between square mils and square thous:
To convert square mils to square thous, multiply the value in square mils by 1. To reverse, multiply square thous by 1.
How to use this converter
Type a value into the calculator. The result in square thous updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Square Thou to Square Mil converter for the reverse direction.
Step-by-step: convert square mils to square thous
- Write down the value in square mils (mil²).
- Multiply that value by the factor 1.
- The product is the equivalent value in square thous (thou²).
- To reverse, multiply the square thou value by 1.
Worked examples
Example 1 — Convert 1 mil² to thou²:
1 × 1 = 1 thou²
Example 2 — Convert 100 mil² to thou²:
100 × 1 = 100 thou²
Real-world example — Molecular dimensions
The diameter of small molecular structures (around 2 square mils) is often converted into related sub-micron units when comparing measurements across different microscopy techniques or imaging modalities.
2 mil² × 1 = 2 thou²
Real-world example — Wavelengths across the spectrum
Optical and atomic-scale phenomena are routinely cross-converted between sub-micron units. A photon of wavelength 800 square mils can be re-expressed in square thous for direct comparison with another instrument's calibration data sheet.
800 mil² × 1 = 800 thou²
Square Mil to Square Thou conversion table
Standard reference values for converting square mils to square thous:
| Square Mil [mil²] | Square Thou [thou²] |
|---|---|
| 0.01 | 0.01 |
| 0.1 | 0.1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
| 4 | 4 |
| 5 | 5 |
| 10 | 10 |
| 20 | 20 |
| 30 | 30 |
| 40 | 40 |
| 50 | 50 |
| 100 | 100 |
| 500 | 500 |
| 1000 | 1000 |
Frequently asked questions
How many square thous is 1 square mil?
How do I convert square mils to square thous?
How do I convert square thous back to square mils?
How many square thous is 100 square mils?
Popular area unit conversions
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Metric / SI (5 units)
Imperial / US Customary (14 units)
Sources & references
Conversion factor (1 mil² = 1 thou²) 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.