Cubic inches to fluid ounces (in³ to fl oz) converter

What is a cubic inches to fluid ounces converter?

A cubic inches to fluid ounces converter is an online tool that translates a volume expressed in cubic inches (in³) into US fluid ounces (fl oz), and back again. The cubic inch is a unit of the US customary and imperial systems based on a cube one inch on each side, and it is often used to describe engine displacement, container capacity, and the size of small parts. The fluid ounce, by contrast, is a unit of liquid measure used for beverages, cooking, and household products. Because one describes a solid geometric volume and the other a liquid measure, moving between them is a common need whenever a capacity given in cubic inches has to be read off as a familiar quantity of liquid.

How it works

Both cubic inches and US fluid ounces describe the same physical quantity — volume — so converting between them is simply a matter of applying a fixed ratio. One cubic inch equals about 16.3871 milliliters, while one US fluid ounce equals about 29.5735 milliliters. Dividing those two figures gives the conversion factor: one cubic inch is roughly 0.55411 US fluid ounces, and one US fluid ounce is roughly 1.80468 cubic inches. The converter performs this multiplication for you in real time, in either direction, so you can type a value into either field and read the equivalent immediately.

Formula for conversion

To convert from cubic inches to US fluid ounces, multiply by the conversion factor:

$\text{fl oz} = \text{in}^3 \times 0.55411$

To convert from US fluid ounces back to cubic inches, multiply by the reciprocal factor:

$\text{in}^3 = \text{fl oz} \times 1.80468$

Cubic inches to fluid ounces conversion table

The table below lists common cubic inch volumes alongside their US fluid ounce equivalents:

Examples of conversion

Example 1: A single cubic inch

Convert 1 cubic inch to US fluid ounces using the factor 0.55411:

$1 \text{ in}^3 \times 0.55411 = 0.55411 \text{ fl oz}$

So one cubic inch holds a little over half a fluid ounce.

Example 2: Reversing the conversion

Convert 1 US fluid ounce to cubic inches using the reciprocal factor 1.80468:

$1 \text{ fl oz} \times 1.80468 = 1.80468 \text{ in}^3$

A single fluid ounce occupies just under 1.8 cubic inches.

Example 3: A container’s capacity

A small container has an internal volume of 100 cubic inches. To express that as a familiar liquid measure:

$100 \text{ in}^3 \times 0.55411 = 55.411 \text{ fl oz}$

Example 4: One US gallon

A US gallon is defined as exactly 231 cubic inches. Converting that volume to fluid ounces confirms the well-known relationship:

$231 \text{ in}^3 \times 0.55411 \approx 128 \text{ fl oz}$

This matches the fact that there are 128 US fluid ounces in a US gallon.

Notes

• This converter uses the US fluid ounce (about 29.5735 mL). The imperial (UK) fluid ounce is slightly smaller, at about 28.4131 mL, so results differ if you need imperial units.
• The cubic inch is the same in both the US customary and imperial systems, so only the fluid ounce definition changes between them.
• For everyday estimates, remembering that 1 in³ is just over half a fluid ounce is usually accurate enough.
• The converter accepts decimal inputs and works in both directions, so you can start from whichever value you already know.

Frequently asked questions

How many fluid ounces are in a cubic inch?

One cubic inch contains approximately 0.55411 US fluid ounces. In other words, a cubic inch holds a little more than half a fluid ounce.

How many cubic inches are in a fluid ounce?

One US fluid ounce is equal to approximately 1.80468 cubic inches.

How do I convert 100 cubic inches to fluid ounces?

Multiply 100 by the conversion factor 0.55411, which gives 55.411 US fluid ounces.

Why is one US gallon equal to 128 fluid ounces and 231 cubic inches?

A US gallon is defined as exactly 231 cubic inches, and it also contains exactly 128 US fluid ounces. Converting 231 cubic inches with the factor 0.55411 reproduces the 128 fluid ounce figure, confirming both definitions describe the same volume.

Does this converter use US or imperial fluid ounces?

It uses US fluid ounces, each equal to about 29.5735 milliliters. If you need imperial (UK) fluid ounces, the value will be slightly different because the imperial fluid ounce is about 28.4131 milliliters.

Can I convert fluid ounces back to cubic inches with the same tool?

Yes. The converter is bidirectional — enter a value in either the cubic inches field or the fluid ounces field and the other value updates automatically.