Frequently Asked Questions
What is the formula for cubic inches of a cylinder?
Volume in cubic inches equals π × r² × h, where r is the radius (half the diameter) in inches and h is the height or length in inches. This calculator asks for diameter, so it divides by 2 internally to get the radius before squaring it.
How do I convert cubic inches to gallons, cubic feet, or liters?
Divide cubic inches by 231 to get US gallons, divide by 1,728 to get cubic feet, or multiply by 0.0163871 to get liters. This calculator performs all three conversions automatically alongside the cubic-inch result.
What happens if I enter the radius instead of the diameter?
The result will be wrong. This calculator expects diameter (the full width across the circle) and halves it internally to get the radius. Entering the radius by mistake halves the true radius again, and since radius is squared in the formula, the computed volume ends up only one quarter of the actual volume.
My measurements are in centimeters or millimeters — how do I use this calculator?
Convert both diameter and height to inches first, since the formula and outputs assume inch measurements throughout. Divide centimeters by 2.54, or millimeters by 25.4, to get inches before entering the values.
Understanding cubic inches of a cylinder
A cylinder's volume is the area of its circular cross-section multiplied by its height. The circle's area is π × r², so multiplying by the height h gives the standard formula V = π × r² × h. Enter the diameter (not the radius) and the height, both in inches — the calculator halves the diameter to get r before applying the formula, so there is no need to do that conversion yourself.
Converting the result
Cubic inches are a small unit, so this calculator also converts the same volume into cubic feet (divide by 1,728), US gallons (divide by 231), and liters (multiply by 0.0163871). That makes it easy to compare a computed volume against a tank capacity, shipping spec, or container size given in a different unit, without doing the conversion arithmetic by hand.