How to convert square millimeters to square inches
To convert a measurement in square millimeters to square inches, multiply the value by 0.0015500031. The conversion factor comes from the relationship between both units and the square meter.
For example, to convert 5 mm² to square inches: 5 × 0.0015500031 = 0.0077500155 in².
What is a square millimeter?
A square millimeter is a metric unit of area equal to the area of a square one millimeter on each side, or one millionth of a square meter. The square millimeter is the go-to unit for very small cross-sections, most notably the gauge of electrical wires and the area of tiny mechanical components.
Common uses of square millimeters include: Electrical wire cross-section (cable gauge); Precision engineering and machining; Cross-sectional area of small parts; Microscopy and materials science.
What is a square inch?
A square inch is an imperial and US customary unit of area equal to the area of a square one inch on each side, exactly 6.4516 square centimeters. The square inch is used for small areas in the US and UK, notably in engineering where pressure is measured in pounds per square inch (psi), one of the most common pressure units in the world.
Common uses of square inches include: Pressure measurement (pounds per square inch); Print and display area; Small material and gasket areas; Product surface and packaging specs.
Square Millimeters to square inches worked examples
Here are some common values converted:
1 mm² = 0.0015500031 in² 5 mm² = 0.0077500155 in² 10 mm² = 0.015500031 in² 50 mm² = 0.077500155 in² 100 mm² = 0.155000310001 in²
Frequently asked questions
How many square inches are in one square millimeter?
One square millimeter (mm²) equals 0.0015500031 square inches (in²). Multiply any value in square millimeters by 0.0015500031 to convert to square inches.
How do I convert square millimeters to square inches?
Multiply the value in square millimeters by 0.0015500031. For example, 5 mm² × 0.0015500031 = 0.0077500155 in².
How do I convert square inches to square millimeters?
Multiply the value in square inches by 645.16, or divide by 0.0015500031. Use the swap button on the converter above to reverse the direction.
Is the square millimeter to square inch conversion exact?
Yes. Area conversions derive from the exact 1959 international definitions of the meter, yard, and foot, so the factors are exact.
What is the formula for square millimeters to square inches?
The formula is: in² = mm² × 0.0015500031. This comes from the definition of both units relative to the square meter.