To calculate the cubic inches inside a jar or other cylinder shaped object, you will need to know the diameter and height of the jar then apply the following formula:

Let's say our jar is 8 inches in diameter and 12 inches in height.

- Half of the circle's diameter equals it's radius (8 / 2 = 4)
- Square the radius (4 * 4 = 16)
- Multiply the height by the squared radius (16 * 12 = 192)
- Multiply that by pi 3.1416 (192 * 3.1416 = 603.1872)

So we know our jar is 603.1872 cubic inches.

If we needed to know how many cubic feet, we would divide cubic inches by 1728.

For reference, here are some common jar dimensions:

- Ball 16 oz Pint Mason Jar dimensions are 5.2 height by 3.2 diameter
- Ball 32 oz Quart Mason Jar dimensions are 6.9 height by 3.9 diameter