# Cubic Inches to Gallons Converter URL: https://speedycalculator.com/calculators/conversion/cubic-inches-to-gallons/ Last updated: 2026-10-25 > Convert cubic inches (in³) to US gallons (US gal): 1 cubic inch = 0.0043290043 US gal, so multiply by 0.0043290043 or divide by 231. Both fields are editable, so you can also type in US gallons and get cubic inches back. ## Inputs - Cubic inches (in³) ## Results - US gallons ## Formula ``` 1 in³ = 0.0043290043 US gal 1 US gal = 231 in³ US gal = in³ × 0.0043290043 ``` ## Explanation The U.S. gallon is defined as exactly 231 cubic inches. Engine displacements, tank sizes and container capacities in cubic inches convert directly. ### How to use the Cubic Inches to Gallons Converter - Type the number of cubic inches into the **Cubic inches** field. Decimals such as 115.5 are fine. - Read the answer in **US gallons** – it updates as you type, with no button to press. - To convert the other way, type into **US gallons** and the cubic inches are recalculated. - Press **Copy results** to copy both values with the page title, or **Copy link** to share this exact conversion. This page converts only in³ ⇄ US gal. Need a different unit? Use the general volume converter, where you can choose any “from” and “to” unit. ### How it works Both units measure volume, so they are always in the same ratio: one cubic inch equals 0.0043290043 US gallons. The calculator multiplies the number of cubic inches you type by 0.0043290043 to give US gallons, and when you type into the US gallons field it divides by the same factor to give cubic inches. Because the ratio never changes, doubling the cubic inches always doubles the US gallons. Results are calculated at full precision and rounded only for display (up to eight decimal places, with very large or small values shown in scientific notation). ### How to convert cubic inches to US gallons - Write down the value in cubic inches, for example **231 in³**. - Multiply by the conversion factor 0.0043290043 (because 1 cubic inch = 0.0043290043 US gal). - 231 × 0.0043290043 = **1 US gal**. - To go back from US gallons to cubic inches, divide by 0.0043290043 – or multiply by 231. ### in³ to US gal conversion table Cubic inchesUS gallonsUS gallonsCubic inches1 in³0.0043290043 US gal1 US gal231 in³57.75 in³0.25 US gal2 US gal462 in³100 in³0.43290043 US gal5 US gal1,155 in³231 in³1 US gal10 US gal2,310 in³350 in³1.5151515 US gal20 US gal4,620 in³500 in³2.1645022 US gal50 US gal11,550 in³1,000 in³4.3290043 US gal100 US gal23,100 in³1,728 in³7.4805195 US gal1,000 US gal231,000 in³ ### What is a cubic inch? A cubic inch is about 16.39 mL. The U.S. gallon is defined as exactly 231 cubic inches, and classic American engine sizes are given in cubic inches (e.g. 350 ci). ### What is a US gallon? The U.S. liquid gallon is exactly 231 cubic inches, about 3.785 litres. It is used for fuel, milk, water and paint in the United States. ### Quick mental conversion For a fast estimate, multiply cubic inches by about **0.0043** to get US gallons; the error is about 0.7%. Use the calculator above when you need the exact figure. ### Common mistakes to avoid Mixing u.s. and uk gallons, pints and fluid ounces, assuming a cup is always 250 ml, and treating volume and weight as interchangeable for anything except water. ## Worked example Inputs — Cubic inches: 231 in³. Results — **US gallons = 1 US gal**. ## FAQ **How many cubic inches in a gallon?** Exactly 231. **How many gallons is 1,000 in³?** About 4.33 US gal. **How many US gallons are in one cubic inch?** 1 in³ = 0.0043290043 US gal. **How many cubic inches are in one US gallon?** 1 US gal = 231 in³. **How do I convert cubic inches to US gallons?** Multiply the number of cubic inches by 0.0043290043. For example, 231 in³ × 0.0043290043 = 1 US gal. **How do I convert US gallons back to cubic inches?** Divide by 0.0043290043 (or multiply by 231), or simply type the value into the US gallons field above. **What is 100 in³ in US gallons?** 100 in³ = 0.43290043 US gal. **What is 1,000 in³ in US gallons?** 1,000 in³ = 4.3290043 US gal. **Is this conversion exact?** Yes. The factor comes from the official definitions of both units (NIST and the SI), so the only difference you may see is rounding in the last displayed digit. **Can I convert to other units on this page?** This page converts only between cubic inches and US gallons. To pick any volume unit, use the general volume converter linked under Related calculators. **What formula does the Cubic Inches to Gallons Converter use?** 1 in³ = 0.0043290043 US gal. ## Sources - [NIST Special Publication 811 – Guide for the Use of the International System of Units](https://www.nist.gov/pml/special-publication-811) - [NIST Handbook 44 Appendix C – General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)