Convert Square Millimeter to Square Thou
Convert square millimeters to square thous instantly. 1 square millimeter = 1550.0031000062 square thou — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Square Thou to Square Millimeter converter for the reverse conversion.
Units explained
Square Millimeter
A square millimeter is a metric unit of area equal to 10⁻⁶ m² (1 mm × 1 mm). It is widely used in engineering, electronics, and small-scale technical work.
Derived by squaring the millimeter, defined as 1/1000 of a meter. The milli- prefix comes from the Latin 'mille' (thousand).
Square millimeters express PCB trace cross-sections, the area of small mechanical features in CAD drawings, biological sample sizes, and material thicknesses.
Millimeter has been part of the metric system since 1795.
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 Millimeter to Square Thou conversion formula
The relationship between square millimeters and square thous:
To convert square millimeters to square thous, multiply the value in square millimeters by 1550.0031000062. To reverse, multiply square thous by 0.00064516.
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 Millimeter converter for the reverse direction.
Step-by-step: convert square millimeters to square thous
- Write down the value in square millimeters (mm²).
- Multiply that value by the factor 1550.0031000062.
- The product is the equivalent value in square thous (thou²).
- To reverse, multiply the square thou value by 0.00064516.
Worked examples
Example 1 — Convert 1 mm² to thou²:
1 × 1550.0031000062 = 1550.0031000062 thou²
Example 2 — Convert 100 mm² to thou²:
100 × 1550.0031000062 = 155000.31000062 thou²
Real-world example — Infrared to visible-spectrum mapping
A 10-square millimeter thermal infrared wavelength corresponds to a much larger number in square thous, the unit favoured for ultraviolet and visible-light specifications.
10 mm² × 1550.0031000062 = 15500.031000062 thou²
Real-world example — Mid-micron to nanometer
3 square millimeters equals 3,000 square thous — useful when relating mid-infrared wavelengths (typically quoted in microns) to nanometer-scale visible-light wavelength tables.
3 mm² × 1550.0031000062 = 4650.0093000186 thou²
Real-world example — From microns to sub-micron features
One square millimeter equals one thousand square thous — the conversion semiconductor designers do constantly when comparing mask feature dimensions to actual transistor gate lengths.
1 mm² × 1550.0031000062 = 1550.0031000062 thou²
Square Millimeter to Square Thou conversion table
Standard reference values for converting square millimeters to square thous:
| Square Millimeter [mm²] | Square Thou [thou²] |
|---|---|
| 0.01 | 15.5000310001 |
| 0.1 | 155.0003100006 |
| 1 | 1550.0031000062 |
| 2 | 3100.0062000124 |
| 3 | 4650.0093000186 |
| 4 | 6200.0124000248 |
| 5 | 7750.015500031 |
| 10 | 15500.031000062 |
| 20 | 31000.062000124 |
| 30 | 46500.093000186 |
| 40 | 62000.124000248 |
| 50 | 77500.15500031 |
| 100 | 155000.31000062 |
| 500 | 775001.5500031 |
| 1000 | 1550003.1000061999 |
Frequently asked questions
How many square thous is 1 square millimeter?
How do I convert square millimeters to square thous?
How do I convert square thous back to square millimeters?
How many square thous is 100 square millimeters?
Popular area unit conversions
Convert Square Millimeter to other area units
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Metric / SI (15 units)
Imperial / US Customary (15 units)
US Survey (5 units)
Indian Subcontinent (16 units)
Other Regional (10 units)
Scientific / Physics (5 units)
Sources & references
Conversion factor (1 mm² = 1550.0031000062 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.