Vertical Tank Volume Calculator: Gallons from Dimensions

Updated 8 November 2026 · Standard formula, shown below

Capacity 564.02 US gal

Volume: 75.40 ft³; Result
Volume: 2,135.04 L; Result
Tank diameter: 48 in; You entered

A vertical tank volume calculator estimates how many gallons a cylindrical tank holds from its diameter and straight-side height. Enter both measurements in inches, and it returns the tank’s volume in US gallons, along with its equivalent in cubic feet and liters.

Formula

A straight-sided vertical cylindrical tank has volume equal to the area of its circular base multiplied by its height. For measurements in inches, the formula for US gallons is:

Gallons = π × (d ÷ 2)² × h ÷ 231

d = inside tank diameter, in inches.
h = inside straight-side liquid height, in inches.
π ≈ 3.14159.
231 = cubic inches in one US liquid gallon.

The helper outputs express that same volume in cubic feet and liters. One cubic foot is 1,728 cubic inches, and one cubic inch is exactly 0.016387064 liters. The gallon result is in US liquid gallons, not Imperial gallons; one US gallon is about 3.785 liters.

Worked Example

Using the calculator’s default dimensions—a 48-inch inside diameter and a 72-inch straight-side height:

Radius = 48 ÷ 2 = 24 inches.
Base area = π × 24² = π × 576 square inches.
Volume = π × 576 × 72 = 130,241.76 cubic inches, approximately.
Gallons = 130,241.76 ÷ 231 = 563.82 US gallons, rounded to two decimal places.

The same volume is 75.37 cubic feet and approximately 2,134.72 liters. These figures describe the ideal cylindrical volume, not necessarily the safe working capacity or the amount you should fill the tank with.

How to Measure a Vertical Tank

Use the tank’s inside dimensions whenever possible. Wall thickness makes the outside diameter larger than the internal diameter, and using the outside measurement overstates capacity. Measure the diameter straight across the circular interior through its center, rather than around the circumference. If you can only measure circumference, diameter is circumference divided by π.

Measure height along the straight cylindrical wall, from the interior bottom to where the cylindrical side ends. Do not include a domed, conical, or rounded top or bottom in this cylinder calculation. If the tank has a level scale, use the liquid depth—not the tank’s full height—to estimate the current amount.

Keep all dimensions in the same unit before applying a formula.
For a partially filled tank, enter the liquid depth as h.
For a tank with internal fittings or a significant sump, remember that the simple formula does not subtract their displacement.

Capacity Versus Usable Volume

Geometric capacity is the volume inside the assumed shape. A tank’s nameplate capacity, rated capacity, or practical fill limit may differ. Manufacturers may account for headspace, structural limits, sloped bottoms, fittings, or other design details. Leave room for expansion, splashing, venting, and safe operation as applicable to the tank and its contents; do not treat the calculator’s full-volume result as a recommended fill line.

Many tanks are not perfect cylinders. A flat-bottom tank with a flat top is the closest match, but dished, elliptical, conical, or sloped ends change the total capacity. For a cylinder with a simple cone-shaped bottom, for example, calculate the cylindrical and conical sections separately and add them. For complex shapes, use the manufacturer’s capacity chart or reliable level-to-volume table.

Estimating Gallons at a Liquid Level

For a vertical cylinder with a flat bottom, liquid volume is proportional to liquid depth: half the straight-side depth corresponds to half the cylindrical volume. Put the current liquid depth in place of h to estimate gallons at that level. This direct relationship does not apply across a curved or sloped bottom, where the tank’s cross-section changes with height.

For example, a 72-inch-high cylindrical section filled to 36 inches holds half the cylindrical section’s capacity, provided the bottom is flat and the measurement is taken from the inside bottom. A level reading alone may not be enough if the tank’s bottom shape is unknown.

Common Errors and Limits

Using radius as diameter: The formula halves the diameter to get radius. Entering a radius as the diameter makes the calculated volume one quarter of the correct value.
Mixing units: This calculator expects inches. Do not enter feet or centimeters without converting; 1 foot is 12 inches and 1 inch is 2.54 centimeters.
Confusing gallon types: US and Imperial gallons are different. The output uses US liquid gallons.
Rounding too early: Keep full precision during calculations, then round the final result. Actual measurements also have some uncertainty.
Assuming all tanks are cylinders: A rectangular tank, horizontal cylinder, or tank with shaped ends needs a different formula or a segmented calculation.

The formula is a geometric estimate. It does not determine a tank’s pressure rating, material compatibility, structural safety, or appropriate operating fill level. Follow the tank maker’s specifications and use equipment suited to the stored material.

Frequently Asked Questions

How do I calculate gallons in a vertical cylindrical tank?
Multiply π by the square of the inside radius, then multiply by the inside liquid height. With dimensions in inches, divide the result in cubic inches by 231 to get US gallons.

How many gallons are in a vertical tank 48 inches wide and 72 inches tall?
If those are inside dimensions of a straight-sided cylinder, its geometric capacity is about 563.82 US gallons. The usable or rated capacity may be lower.

Does tank diameter mean the radius?
No. Diameter is the full distance across the circular tank through its center. Radius is half the diameter; use that halved value in the squared part of the formula.

Can I use outside measurements?
You can, but the result will generally overestimate internal capacity because the tank walls take up space. Inside measurements give a better estimate.

How do I calculate gallons from a liquid level?
For a flat-bottom vertical cylinder, use the liquid depth from the inside bottom as the height in the formula. Curved or sloped bottoms require a shape-specific calculation or a calibration chart.

Formula used

in d | Tank diameter | in | 48 | 0
in h | Straight-side height | in | 72 | 0
out gal | Capacity | US gal | pi * (d / 2)^2 * h / 231 | 2
out ft3 | Volume | ft³ | pi * (d / 2)^2 * h / 1728 | 2
out l | Volume | L | pi * (d / 2)^2 * h * 0.016387064 | 2

Each line is one input (in, sel, list) or one result (out: label, unit, formula, decimals). How the calculators work

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.