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Tank Volume Calculator

Construction

Calculate a cylindrical storage tank's volume in gallons and cubic feet from its diameter and height. Ideal for water, fuel, and chemical storage tanks.

Reviewed by the thecalcu.com team · Last updated July 24, 2026

2240
2600

Volume (gallons)

94
Volume (cubic feet)
12.57

This calculator computes your Volume (gallons), Volume (cubic feet) from the values you enter.

Inputs
Diameter (in)Height (in)
Outputs
Volume (gallons)Volume (cubic feet)

What is a Tank Volume?

A Tank Volume Calculator computes the total water or liquid capacity of a vertical cylindrical storage tank in gallons and cubic feet, based on its diameter and height. Enter the two dimensions exactly as they appear on a tank's spec sheet or nameplate, typically in inches, and the calculator applies the standard cylinder volume formula to return an accurate capacity figure.

This is the same underlying geometry used for pressure tanks, cisterns, fuel tanks, chemical storage vessels, and any other upright cylindrical container.

Why Use a Tank Volume Calculator?

Knowing a tank's exact capacity matters for sizing pumps, calculating fill times, dosing water treatment chemicals correctly, and verifying that a tank meets a required storage capacity before purchase or installation. Manually computing cylinder volume, converting inches to feet, squaring a radius, multiplying by pi, then converting cubic feet to gallons, introduces several opportunities for arithmetic error.

This calculator handles the full conversion chain in one step. If your project also involves moving liquid through pipe to or from the tank, pair this result with the Pipe Volume Calculator to understand total system capacity, or the Liters per Minute Calculator to estimate fill time at a known flow rate.

Who Should Use This Calculator?

Homeowners and well system owners sizing or verifying a pressure tank's capacity can confirm the tank meets their system's drawdown requirements before installation.

Plumbers and irrigation contractors specifying cisterns, holding tanks, or rainwater harvesting systems need accurate capacity figures to match tank selection to a project's storage requirements.

Facilities and maintenance staff managing fuel, chemical, or process water storage tanks use volume calculations for inventory tracking, chemical dosing ratios, and regulatory reporting.

Hobbyists and small-scale brewers or aquarists building or buying cylindrical tanks for aquaculture, brewing, or storage applications can quickly verify a tank's true capacity against their space and volume needs.

What Insights Does the Tank Volume Calculator Give You?

The calculator returns two outputs: Volume (gallons), the primary highlighted result showing the tank's total capacity in US gallons, and Volume (cubic feet), the same capacity in cubic feet for cross-checking or use in specifications that reference that unit.

Diameter has a much larger effect on total volume than height does, since volume scales with the square of the radius but only linearly with height. When comparing two tank options with similar overall size, the wider one will typically hold noticeably more than a taller, narrower alternative, worth checking carefully if you're choosing between tank shapes for a fixed capacity target.

How to use this Tank Volume calculator

  1. Find your tank's diameter in inches, either from the manufacturer's spec sheet, nameplate, or a direct measurement across the tank's widest circular point.

  2. Find your tank's height in inches, measured from the base to the top of the cylindrical section (excluding any domed cap if present).

  3. Enter Diameter (in) using the slider or number field.

  4. Enter Height (in) using the slider or number field.

  5. Read your Volume (gallons) in the highlighted result card, this is your tank's total estimated capacity.

  6. Check Volume (cubic feet) if you need the figure in cubic feet for a spec sheet comparison or downstream calculation.

Show formula & methodology ↓Show less ↑

Formula & Methodology

The calculator uses the standard cylinder volume formula, converted to inches-based tank specifications:

Step 1, Convert diameter and height to feet:

> r (ft) = Diameter (in) ÷ 24
> h (ft) = Height (in) ÷ 12

Step 2, Compute volume in cubic feet:

> Volume (ft³) = π × r² × h

Step 3, Convert to gallons:

> Volume (gal) = Volume (ft³) × 7.4805

Worked example:

- Diameter = 24 in → radius = 24 ÷ 24 = 1.0 ft
- Height = 48 in → height = 48 ÷ 12 = 4.0 ft
- Volume (ft³) = π × 1.0² × 4.0 = 12.57 ft³
- Volume (gal) = 12.57 × 7.4805 = 94.0 gallons

For related capacity calculations, see the Pipe Volume Calculator and the Pool Calculator.

Frequently Asked Questions

Why are the inputs in inches while the output is in gallons?
Tank diameter and height are almost always specified by manufacturers in inches, since most storage tanks are compact enough that inches give a more precise, practical measurement than feet. The calculator converts internally to feet for the cubic-feet calculation and then to gallons, so you can enter the dimensions exactly as listed on a spec sheet.
How much water does a 24-inch diameter, 48-inch tall tank hold?
A cylindrical tank with a 24-inch diameter and 48-inch height holds approximately 117.4 gallons (about 15.7 cubic feet). This is a common size for residential pressure tanks and small storage applications.
Does this calculator work for horizontal cylindrical tanks?
This calculator assumes a vertical, upright cylindrical tank where height runs along the cylinder's axis. For a horizontal tank lying on its side, the same total volume formula applies if the tank is completely full, but partial-fill volume calculations for a horizontal tank require a different, more complex formula that accounts for the curved cross-section.
How do I measure tank diameter accurately?
Measure across the widest point of the tank's circular cross-section, ideally at multiple points around the circumference to confirm it's a true circle, and use the inner diameter if you have access to it. For sealed tanks, the manufacturer's spec sheet or nameplate is usually the most reliable diameter source.
Why does tank volume increase so much with diameter compared to height?
Volume depends on the square of the radius but scales linearly with height, so a tank with double the diameter (at the same height) holds four times as much, while a tank with double the height (at the same diameter) only holds twice as much. Diameter has a much larger effect on total capacity than height does.
What's a typical tank size for residential water storage?
Common residential pressure and holding tanks range from around 20 gallons for small point-of-use applications up to 500 to 1,000+ gallons for whole-house cisterns or rainwater harvesting systems, with diameters commonly between 16 and 48 inches depending on capacity and available installation space.
How is this calculator different from the Pipe Volume Calculator?
Both use the same cylinder volume formula, but the Tank Volume Calculator is designed for compact, upright storage vessels with inputs in inches for both diameter and height, while the Pipe Volume Calculator is designed for long, thin runs of pipe with diameter in inches and length in feet, matching how each is typically specified and measured.
Can this calculator handle fuel or chemical storage tanks?
Yes, the geometric volume calculation applies to any cylindrical tank regardless of the liquid stored. Just note that the gallons figure represents total tank capacity in US liquid gallons; converting to weight for fuel or chemicals requires multiplying by that specific liquid's density, which differs from water.
How accurate is this calculator for tanks with rounded or domed tops?
The calculator assumes a straight-sided cylinder for the full entered height. If your tank has a rounded, domed, or conical top or bottom section, the true volume will be somewhat less than the calculated figure for a pure cylinder of the same overall height, since the curved cap holds less volume than an equivalent straight cylindrical section.
Why is the gallons-per-cubic-foot conversion factor 7.4805?
One US gallon is defined as exactly 231 cubic inches. Since one cubic foot equals 1,728 cubic inches, dividing 1,728 by 231 gives approximately 7.4805 gallons per cubic foot, the standard conversion factor used throughout US plumbing and tank capacity calculations.
How do I calculate how full my tank currently is, not just total capacity?
To estimate partial fill, measure the height of liquid currently in the tank rather than the tank's full height, and enter that measured liquid height into the calculator instead of the tank's total height. The result will represent the volume of liquid currently present rather than the tank's maximum capacity.
What tank sizes are common for septic or holding tank applications?
Septic and larger holding tanks are typically much larger than pressure tanks, often ranging from 500 to 1,500+ gallons for residential septic tanks, with correspondingly larger diameters (often 48 to 96 inches) and heights, though these are frequently horizontal cylindrical or rectangular rather than upright cylindrical designs.
Also known as
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