Gallons per Square Foot Calculator

Created by Krishna Nelaturu
Reviewed by Steven Wooding
Last updated: Oct 18, 2022

Welcome to our gallons per square foot calculator, the perfect tool to convert square feet to gallons and gallons to square feet. If you're building a swimming pool or an aquarium and wish to calculate how many gallons of water per square foot you need, you've come to the right place!

In this article, we shall discuss the basic conversion involved and answer a few questions, including:

  • What is a gallon?
  • How many gallons in one square foot?
  • How many square feet in a gallon?

If you're exclusively interested in calculating how many gallons of paint you require, use our paint calculator.

What is a gallon?

A gallon is a unit of volume commonly used in the United States. There are three kinds of gallons in use nowadays:

  • The imperial gallon, also called the UK gallon, equals 4.54609 liters of volume (or 8 pints). We denote this with the symbol UK gal\text{UK gal};

  • The US gallon equals 3.785411784 liters (231 cubic inches). We denote this with the symbol US gal\text{US gal}; and

  • The US dry gallon equals ⅛ of a US bushel. We denote this as usdrygal\text{usdrygal}.

We shall curtail our discussion to US gallons in the following sections.

How many gallons in one square foot?

There are 7.48052 gallons in one cubic foot. To verify this conversion rate, use our volume conversion tool.

Let's consider a cuboid with a base area A ft2A \text{ ft}^2 and a height H ftH \text{ ft} . To figure out how many gallons are in one square foot, start by converting its volume V ft3V \text{ ft}^3 from  ft3\text{ ft}^3 to US gal\text{US gal}:

Vol in US gal=V ft3×7.48052 US gal/ft3US gal/ft2=V ft3A ft2×7.48052 US gal/ft3US gal/ft2=A ft2×H ftA ft2×7.48052 US gal/ft3US gal/ft2=H ft×7.48052 US gal/ft3\scriptsize\begin{align*} &\text{Vol in US gal} = V\text{ ft}^3 \times 7.48052 \text{ US gal/ft}^3\\[1em] &\text{US gal/ft}^2 = \frac{V \text{ ft}^3}{A\text{ ft}^2} \times 7.48052 \text{ US gal/ft}^3\\[1em] &\text{US gal/ft}^2 = \frac{A\text{ ft}^2\times H\text{ ft}}{A\text{ ft}^2} \times 7.48052 \text{ US gal/ft}^3\\[1em] &\text{US gal/ft}^2 = H\text{ ft} \times 7.48052 \text{ US gal/ft}^3\\ \end{align*}

In other words, the volume in gallons contained in one square foot depends on the object's height. Specifically, it is 7.48052 times the object's height expressed in feet.

🙋 It is evident that to convert square feet to gallons, we must multiply the quantity US gal/ft2\text{US gal/ft}^2 with the base area A ft2A \text{ ft}^2, which is the same as calculating the volume in  ft3\text{ ft}^3 and converting it into  US gal\text{ US gal}. Inverting this process, we can convert gallons to square feet.

How many square feet in a gallon?

One US gallon equals 0.133681 cubic feet of volume. Using this conversion rate, let's start with the same cuboid we introduced in the previous section. Following similar steps as before, we would get:

Vol in ft3=V US gal×0.133681 ft3/US galft2/US gal=1H ft×0.133681 ft3/US gal\scriptsize\begin{align*} &\text{Vol in ft}^3 = V\text{ US gal} \times 0.133681 \text{ ft}^3/ \text{US gal}\\[1em] &\text{ft}^2/\text{US gal} = \frac{1}{H\text{ ft}} \times 0.133681 \text{ ft}^3/ \text{US gal}\\ \end{align*}

This result is inevitable, considering our previous answer. Note that the square feet per gallon are inversely proportional to the object's height in feet.

Our area conversion tool can help you convert areas from different units.

Calculating gallons of water per square foot

An important application of this concept pertains to how many gallons of water are in a square foot of a tank, pool, or any other container. You can confidently answer that it depends on the container's height in feet.

Vwater=H×7.48052\small V_{\rm{water}} = H \times 7.48052

where:

  • VwaterV_{\rm{water}} is the gallons of water in one square foot of the container;
  • HH is the height of the container in feet; and
  • 7.480527.48052 is the conversion rate of volume from cubic feet to gallons.

This calculation is valid for any liquid, not just water.

How to use this gallons per square foot calculator

This gallon per square foot calculator is a versatile and easy-to-use tool. To convert square feet to gallons and to calculate how many gallons per square foot:

  1. Enter the base area, preferably in square feet. If it is not possible, select the correct unit before entering the value.
  2. Input the height or depth of the container in your unit of choice. The calculator will show you the Gallons per square foot and the volume in gallons.

If you only have the length and width of the base, select advanced mode below our gallons per square foot calculator and enter these values to calculate the area.

To convert gallons to square feet:

  1. Enter the volume, preferably in US gallons. If it is not possible, select the correct unit before entering the value.
  2. Input the height or depth of the container in your unit of choice. The calculator will show you the area in square feet.

FAQ

How do I convert 20 gallons to square feet?

To convert 20 gallons to square feet, you need to know the container’s height (or depth) H :

  1. Convert the height H into feet to get H ft.
  2. Multiply H ft with 7.48052 to get gallons per square foot G = H ft × 7.48052.
  3. Divide the volume of 20 US gal by the gallons per square foot G to convert it to square feet, 20/G ft2.
  4. Verify your result using our gallons per square foot calculator.

How many gallons of water in a square foot?

It depends on the height H of the water from the base. To calculate gallons of water per square foot, follow these steps:

  1. Convert the height H into feet to get H ft.
  2. Multiply H ft by 7.48052 to get gallons of water in one square foot: G = H ft × 7.48052.
  3. Confirm your result using our gallons per square foot calculator.

How many gallons of water per square foot does the Mariana Trench have?

There are 269,576 US gal/sq. ft of water at the Mariana Trench at its maximum known depth of 36,037 ft. To calculate this answer yourself, follow these simple steps:

  1. Multiply the depth 36037 ft by 7.48052 to get the gallons of water in one square foot 36037 ft × 7.48052 = 269,575.5 US gal/sq. ft.
  2. Verify this result using our gallons per square foot calculator.

How do you convert gallons per square foot to gallons per square meter?

To convert gallons per square foot to gallons per square meter, multiply the value with the conversion rate 10.7639. You can verify this conversion using our area converter.

Krishna Nelaturu
Area in square feet
ft²
Height
ft
Gallons per square foot
US gal
/ sq.ft
Volume
US gal
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