Square millimeters to Square inches converter

To convert square millimeters to square inches, enter the value in the first field. The result in square inches is calculated automatically using the exact conversion factor.

1 mm² ≈ 0.00155000310001 in²
1 in² = 645.16 mm²

Formula: in² ≈ mm² × 0.00155000310001
mm² = in² × 645.16

Definitions: 1 mm² = 1 × 10^-6 m²; 1 in² = 0.00064516 m²

The square millimeter (mm²) is the area of a square 1 mm on each side. It is used for the cross-section of electrical wires and cables and for small parts in engineering.

The square inch (in²) is the area of a square 1 inch on each side. It is used in the United States for small surfaces and in engineering, where pressure in psi means pounds-force per square inch.

See the conversion table with commonly used values, handy for quick reference or study.