Cubic inches are the expression of the volume of a threedimensional object. For typical square or rectangular areas, multiple the length of each side in inches, according to Math.com.
A threedimensional object has three sides  often referred to as the object's length, width and depth. Use a ruler to measure each side in inches.
For a square, all three sides are the same. If a rectangular area has sides of 7 inches, 4 inches and 10 inches, multiply these together. The answer is 280.
The answer of 280 is recorded as 280 cubic inches.
You seem to be wanting a conversion into cubic inch, but have not specified from what. Here are two general conversions to cubic inch. 1 cubic centimeter = 0.061 cubic inch. 1 cubic
http://wiki.answers.com/Q/What_is_the_formula_for_...

1 cubic inch is equal to 0.016387064 liters. 1 cubic centimeter is equal to
http://www.chacha.com/question/whatisthecubici...

1. Solve for Q=3*a_1–a_2^2)/9, Read, for example, a_1 as “a sub 1.”. For example, if you want to solve for z in z^3–3z^2–z+3=0, then Q= – 4/3.
http://www.ehow.com/how_5976955_calculatecubicfo...

1 Measure the length, width, and depth of an object in inches. To calculate the volume of a rectangular space, all you need to know are the values of its dimensions in inches. You
http://www.wikihow.com/CalculateCubicInches
