Square Inch (in²) - Unit Information & Conversion
What is a Square Inch?
Definition
The square inch (symbol: in², sq in) is an imperial and US customary unit of area. It represents the area of a square with sides that are each one inch long.
History
Derived from the inch, whose definition has varied historically but was standardized as 25.4 mm, the square inch became a common unit for small area measurements within the imperial system. It is frequently used in the US and UK for engineering and everyday measurements.
Common Uses
- Engineering & Manufacturing (US/UK): Specifying the area of small components, cross-sections, or surface areas.
- Material Measurement: Measuring the area of small sheets of material (e.g., paper, fabric samples).
- Pressure Measurement: Used implicitly in units like pounds per square inch (psi).
- Crafts & Hobbies: Measuring fabric squares, paper sizes, or small design areas.
Unit FAQs
How many square inches are in a square foot?
There are 144 square inches in one square foot (12 inches x 12 inches).
How many square centimeters are in a square inch?
One square inch is equal to exactly 6.4516 square centimeters.
Is the square inch used for large areas?
No, it's used for small areas. Square feet (ft²) or square yards (yd²) are used for room sizes, and acres (ac) or square miles (mi²) for land.
Is the square inch an SI unit?
No, it is part of the imperial and US customary systems. The corresponding metric units are square centimeter (cm²) or square millimeter (mm²).
Square Inch Conversion Formulas
To Square Meter:
To Square Kilometer:
To Square Centimeter:
To Square Millimeter:
To Square Foot:
To Square Yard:
To Square Mile:
To Acre:
To Hectare:
Convert Square Inch
Need to convert Square Inch to other area units? Use our conversion tool.