# How to Calculate Gallons in a Round Tank

Written by irene blake
• Share
• Tweet
• Share
• Pin
• Email

High school mathematics will help you calculate the number of gallons a round tank holds. Just use a simple formula based on the tank's depth and radius. Measure the inside dimensions to calculate the capacity most accurately.

Skill level:
Moderate

### Things you need

• Measuring tape
• Calculator

## Instructions

1. 1

Calculate the radius of the tank. The radius equals the tank's diameter divided by two. (The diameter is the distance from a point on one side of the tank to the point directly opposite.) That means if the diameter is 22 feet, the radius is 11 feet (because 22 divided by 2 equals 11). Convert any partial foot to a decimal. For example, a diameter of 17 feet has a radius of 8.5 feet.

2. 2

Multiply the radius by itself to obtain its square. (For example, if the radius is 11 feet, multiply it by 11 to get 121.)

3. 3

Multiply 3.1417 (pi) by the radius' square. For example, 3.1417 times 121 equals 380.146.

4. 4

Measure the depth. Convert any partial foot to a decimal. Depending on the tank's size, you might need a ladder to stand on.

5. 5

Multiply the result in Step 3 by the depth of the tank to convert the measurements and calculate the tank's capacity in cubic feet. (For example, 380.146 multiplied by a depth of 10 feet gives you 3801.46 cubic feet.)

6. 6

Multiply the result in Step 5 by 7.47. This converts the measurement into gallons. For example, 3801.46 times 7.47 gives you 28,397 gallons (rounded off). This is the water capacity in gallons of a 22-foot-by-10-foot-round tank.

### Don't Miss

• All types
• Articles
• Slideshows
• Videos
##### Sort:
• Most relevant
• Most popular
• Most recent