Calculate Gallons by Square Feet
Have you ever wondered find the number of gallons of water needed to fill an aquarium, pond or tank by using square feet? There are no techniques to determine the number of gallons from square feet because square feet is used to measure area, not volume. But don't be discouraged. By just adding one extra measurement, depth, you will find the answer. Let's use an aquarium as our first example.
Instructions
Filling a fish aquarium
1. To calculate the number of gallons of water to fill a rectangular aquarium, measure all of the dimensions of the aquarium: width, length and depth (height) with a ruler or tape measure. Write the measurements down. Measurements in inches are converted to feet by dividing each by 12 (12 inches equals 1 foot).
2. Use the calculator to find the volume of the aquarium by multiplying width, length and depth (height). The answer will be in cubic feet (ft^3).
3. Take the answer from the Step 2 (in ft^3) and multiply by 7.481. This answer will be the number of gallons you need to fill the aquarium. Remember 1 cubic foot equals 7.481 U.S. gallons. (For the British Imperial System, 1 cubic foot equals 6.23 gallons.)
4. Let's look at an example with real measurements. Find the number of gallons in a rectangular aquarium with the following dimensions:
The width is 4 feet 3 inches, or 51 inches. Dividing 51 by 12 equals 4.25 feet. The length is 2 feet 6 inches, or 30 inches. Divide 30 by 12 equals 2.5 feet. The depth is 2 feet. To find the volume use the formula:
V (volume) = 4.25 x 2.5 x 2 = 21.25 ft^2
Multiply 21.25 square feet by 7.481 = 158.97 gallons. This is your answer.
5. If you have a round tank, measure the diameter (the length across the circle) of the tank. Divide the diameter in half to get the radius. Use the formula A (area) = 3.14 (number pi) x r^2 (radius to the second power). The result will give you the square footage of the surface area.
6. Multiply the answer from Step 5 by the depth of the tank to get the volume in cubic feet. Then multiply by 7.481. The answer is the number of gallons of water you need to fill the round tank.
7. For example, you have a round container with a diameter of 4 feet and depth of 3 feet. Calculate the area of the surface: A (area) = 3.14 x (4/2) ^2 = 12.56 square feet. Find the volume of the container by multiplying the area by the depth of the container.
V (volume) = A (area) x depth = 12.56 x 3 = 37.68 cubic feet. Multiply the volume in cubic feet by 7.481.
37.68 x 7.481= 281.884 gallons. This is your answer.
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