Square Inches to Square Centimeters (in² to cm²)

1 square inch equals 6.4516 square centimeters exactly.

1 square inch = 6.4516 square centimeters

How to convert square inches to square centimeters

To convert square inches to square centimeters, multiply the number of square inches by 6.4516. This factor is exact. To go the other way, multiply square centimeters by 0.15500031 (rounded).

square centimeters = square inches × 6.4516

Example: 10 square inches = 64.516 square centimeters.

About these units

Square Inch (in²)

US & ImperialCurrent unit

A square one inch on a side, exactly 6.4516 cm². Used for small parts and for pressure (pounds per square inch).

Latin uncia, one twelfth, gave English the inch, which Old English borrowed as ynce. A statute of Edward II in 1324 defined it as three barleycorns, dry and round, set end to end, and the barleycorn remained the base for centuries after 1066. The modern square inch rests on a 20th-century agreement: the United States adopted a yard of exactly 0.9144 meter on 1 July 1959, the United Kingdom followed effective 1 January 1964, and the inch became exactly 25.4 mm.

Squaring that gives exactly 6.4516 cm² for one square inch, and one square meter is about 1,550 of them. Its best-known descendant is the pound per square inch, psi, the pressure unit still used for American tires and air tanks: atmospheric pressure at sea level is about 14.7 psi, a car tire is typically inflated to around 32 psi above the surrounding air, and one psi is about 6.895 kilopascals. The square inch itself is common in the US and UK for small parts and printed material.

1 square inch = 0.00064516 square meters (exactly).

Sources: Wikipedia: Square inch; Wikipedia: Inch; Wikipedia: Pounds per square inch

Square Centimeter (cm²)

Metric (SI)Current unit

A square one centimeter on a side; 1/10,000 of a square meter.

Physicists, rather than surveyors, put the centimeter at the center of a measuring system. Carl Friedrich Gauss proposed absolute units based on length, mass and time in 1832, choosing the millimeter, and in 1873 a British Association committee including James Clerk Maxwell and William Thomson (Lord Kelvin) recommended the centimeter, gram and second instead. In that CGS system the square centimeter turns up inside derived units, such as the stokes of kinematic viscosity, defined as one square centimeter per second.

A square centimeter is one ten-thousandth of a square meter, so 10,000 of them fill a square meter. It is a natural size for small flat things: a square inch is exactly 6.4516 cm², and a square foot is exactly 929.0304 cm². Because the CGS system defined force and pressure with the centimeter, the dyne per square centimeter became its unit of pressure, called the barye, which equals 0.1 pascal. SI practice prefers the square meter for large areas and the square millimeter for very small ones.

1 square centimeter = 0.0001 square meters (exactly).

Sources: Wikipedia: Centimetre-gram-second system of units; Wikipedia: Square centimetre; NIST Guide to the SI, Appendix B.8: conversion factors

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