Convert Square Inch to Square Mil
Convert square inches to square mils instantly. 1 square inch = 1000000 square mil — use the live calculator, the exact formula, a conversion table and worked examples. Also check the Square Mil to Square Inch converter for the reverse conversion.
Units explained
Square Inch
A square inch is an imperial unit of area equal to exactly 0.00064516 m², the area of a square with sides of one inch. It is widely used in the United States for small-area measurements.
Derived by squaring the inch. The inch was standardized to exactly 25.4 mm via the 1959 International Yard and Pound Agreement.
Square inches are used extensively in US engineering, manufacturing, real estate (for floor plans), and everyday small-area measurements. Engine displacement is often expressed in cubic inches but cross-sections in square inches.
Inch dates to medieval English usage; modern exact value standardized in 1959.
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 Inch to Square Mil conversion formula
The relationship between square inches and square mils:
To convert square inches to square mils, multiply the value in square inches by 1000000. To reverse, multiply square mils by 1e-6.
How to use this converter
Type a value into the calculator. The result in square mils 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 Mil to Square Inch converter for the reverse direction.
Step-by-step: convert square inches to square mils
- Write down the value in square inches (in²).
- Multiply that value by the factor 1000000.
- The product is the equivalent value in square mils (mil²).
- To reverse, multiply the square mil value by 1e-6.
Worked examples
Example 1 — Convert 1 in² to mil²:
1 × 1000000 = 1000000 mil²
Example 2 — Convert 100 in² to mil²:
100 × 1000000 = 1e+8 mil²
Real-world example — Infrared to visible-spectrum mapping
A 10-square inch thermal infrared wavelength corresponds to a much larger number in square mils, the unit favoured for ultraviolet and visible-light specifications.
10 in² × 1000000 = 1e+7 mil²
Real-world example — Mid-micron to nanometer
3 square inches equals 3,000 square mils — useful when relating mid-infrared wavelengths (typically quoted in microns) to nanometer-scale visible-light wavelength tables.
3 in² × 1000000 = 3000000 mil²
Real-world example — From microns to sub-micron features
One square inch equals one thousand square mils — the conversion semiconductor designers do constantly when comparing mask feature dimensions to actual transistor gate lengths.
1 in² × 1000000 = 1000000 mil²
Square Inch to Square Mil conversion table
Standard reference values for converting square inches to square mils:
| Square Inch [in²] | Square Mil [mil²] |
|---|---|
| 0.01 | 10000 |
| 0.1 | 100000 |
| 1 | 1000000 |
| 2 | 2000000 |
| 3 | 3000000 |
| 4 | 4000000 |
| 5 | 5000000 |
| 10 | 1e+7 |
| 20 | 2e+7 |
| 30 | 3e+7 |
| 40 | 4e+7 |
| 50 | 5e+7 |
| 100 | 1e+8 |
| 500 | 5e+8 |
| 1000 | 1e+9 |
Frequently asked questions
How many square mils is 1 square inch?
How do I convert square inches to square mils?
How do I convert square mils back to square inches?
How many square mils is 100 square inches?
Popular area unit conversions
Convert Square Inch to other area units
Show all Square Inch conversions
Metric / SI (16 units)
Imperial / US Customary (14 units)
US Survey (5 units)
Indian Subcontinent (16 units)
Other Regional (10 units)
Scientific / Physics (5 units)
Historical / Pre-metric European (6 units)
Sources & references
Conversion factor (1 in² = 1000000 mil²) 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.