Question 1

How do I calculate tank volume in gallons?

Accepted Answer

Find the volume in cubic feet, then multiply by 7.48. For a cylinder, volume is π times the radius squared times the height. A 4 ft diameter, 6 ft tall tank holds π × 2² × 6 = 75.4 ft³, or about 564 gallons.

Question 2

How many gallons in a cubic foot?

Accepted Answer

7.48 US gallons. Going the other way, one gallon is 0.1337 cubic feet.

Question 3

How do I calculate the volume of a horizontal cylindrical tank?

Accepted Answer

Total capacity uses the same formula as a vertical one — π r² times the length. Partial fill is harder, because the cross-section of liquid is a circular segment rather than a simple fraction of the height.

Question 4

What size tank do I need for rainwater harvesting?

Accepted Answer

A rough guide: roof area in square feet times rainfall in inches times 0.623 gives gallons per rain event. A 1,500 ft² roof in a 1-inch rain sheds about 934 gallons, so a 1,000-gallon tank fills in a single decent storm.

Question 5

How much does a full water tank weigh?

Accepted Answer

Water weighs 8.34 lb per gallon, so a 500-gallon tank holds about 4,170 lb of water — over two tons — before you count the tank itself. This matters enormously for stands, platforms, and floor loading.

Question 6

What is the difference between US and imperial gallons?

Accepted Answer

An imperial gallon is about 20% larger: 1 US gallon is 0.833 imperial gallons. Tank specifications from UK or Canadian manufacturers may use imperial, which is why the calculator shows both.

Question 7

How do I find the capacity of a tank I cannot see inside?

Accepted Answer

Measure the external dimensions and subtract the wall thickness from each. For a plastic tank, the difference is usually small; for a thick-walled steel or concrete tank, ignoring it can overstate capacity by several percent.

Question 8

How do I calculate the volume of a tank with domed ends?

Accepted Answer

Treat it as a cylinder plus two hemispherical caps: the cylinder gives π r² times its straight length, and two hemispheres together make one sphere, so add 4/3 π r³. Run the cylinder and the sphere separately here and add them.

Tank Volume Calculator

Inputs

Result

Formula

References

Related tools & materials

Calculators

Don't forget

Also useful

Frequently asked questions

Cite this page

Embed on your site