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Cylinder Volume Gallons Calculator

Compute any cylinder's capacity in US or UK gallons. Enter inside diameter and height for an instant, accurate gallon result.

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Cylinder Volume—gallons

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How to Calculate Cylinder Volume in Gallons

Any cylindrical container — from a water storage tank to a chemical drum — holds a volume defined by its circular cross-section and its height. The cylinder volume gallons calculator converts that geometry directly into US liquid gallons or UK imperial gallons, eliminating multi-step unit conversions.

The Core Formula

The standard volume of a right circular cylinder is:

V (cubic inches) = π × r² × h

where r is the radius (half the inside diameter) and h is the height or length, both in inches. To convert cubic inches to US liquid gallons, divide by 231 — the exact cubic-inch equivalent of one US gallon. The complete formula becomes:

Vgal = (π × r² × h) ÷ 231

For UK imperial gallons, the divisor changes to 277.4194 cubic inches per gallon, reflecting the larger imperial measure. According to NIST Selected Procedures for Volumetric Calibrations, precise unit definitions are critical for accurate volumetric measurement in industrial and scientific contexts.

Variable Definitions

  • Diameter (d): The inside diameter measured across the widest interior point. The radius used in the formula equals d ÷ 2.
  • Height / Length (h): For an upright tank, the vertical height from base to top. For a horizontal cylindrical tank, the total length along the central axis.
  • Dimension Unit: Both diameter and height must share the same unit — inches, feet, centimeters, or meters. The calculator converts all inputs to inches before applying the divisor.
  • Gallon Type: US liquid gallon (231 in³) or UK imperial gallon (277.4194 in³). These differ by roughly 20%, so selecting the wrong type produces a significant error.

Step-by-Step Derivation

  1. Measure the inside diameter — the usable interior span, not the outer wall-to-wall distance.
  2. Calculate the radius: r = diameter ÷ 2.
  3. Convert all dimensions to inches if entered in feet, centimeters, or meters.
  4. Compute cubic-inch volume: V = π × r² × h.
  5. Divide by 231 for US gallons or 277.4194 for UK imperial gallons.

Worked Examples

Vertical Storage Tank

A vertical steel tank has an inside diameter of 36 inches and a height of 60 inches.

  • Radius: 36 ÷ 2 = 18 in
  • Volume: π × 18² × 60 = π × 324 × 60 = 61,072.8 in³
  • US gallons: 61,072.8 ÷ 231 = 264.4 gal
  • UK imperial gallons: 61,072.8 ÷ 277.4194 = 220.2 gal

Horizontal Propane Tank

A horizontal cylindrical propane tank measures 24 inches in diameter and 60 inches long.

  • Radius: 24 ÷ 2 = 12 in
  • Volume: π × 12² × 60 = π × 144 × 60 = 27,143.4 in³
  • US gallons: 27,143.4 ÷ 231 = 117.5 gal

Practical Applications

The formula appears across many professional fields. The Tennessee Department of Environment Water Treatment Mathematical Formulas guide uses cylinder volume calculations to determine chemical dosing volumes and tank capacities at municipal water plants. The Wisconsin DSPS Quick Reference Tables for Cylindrical Tanks provide pre-computed gallon figures for standard tank diameters used in boiler and pressure vessel compliance. Additional use cases include:

  • Agriculture: Sizing irrigation storage tanks and liquid fertilizer drums — a 48-inch diameter tank 80 inches tall holds approximately 752 US gallons, suitable for medium-scale farms.
  • HVAC and plumbing: Calculating expansion tank and buffer tank capacity to meet system volume requirements and pressure relief specifications.
  • Chemical processing: Determining batch volumes and reagent storage capacity to ensure proper formulation ratios and inventory control.
  • Aquariums and pools: Estimating water volume for treatment chemical dosing — a 60-inch diameter pool tank 48 inches deep holds roughly 1,173 US gallons.
  • Fuel storage: Computing diesel, gasoline, or propane tank capacity for inventory management and delivery scheduling.

Accuracy Considerations

The formula assumes a perfect right circular cylinder with uniform internal diameter from base to top. Real-world tanks may have domed tops, conical bottoms, internal baffles, or tapered sections that reduce usable volume. For standard manufactured tanks in steel, polyethylene, or fiberglass, the formula typically yields results within ±1% of actual capacity. For legally certified capacity figures required in regulatory compliance, always consult the manufacturer's stamped capacity plate or certified capacity certification.

Unit Conversion Reference

When dimensions are not in inches, apply these multipliers before computing: 1 foot = 12 inches; 1 centimeter = 0.3937 inches; 1 meter = 39.3701 inches. The calculator applies these conversions automatically based on the selected dimension unit, delivering gallon results without any manual intermediate steps.

Reference

Frequently asked questions

How many gallons does a cylinder hold?
The number of gallons a cylinder holds depends on its inside diameter and height. Using the formula V = (π × r² × h) ÷ 231, a cylinder 12 inches in diameter and 24 inches tall holds approximately 14.7 US gallons. A larger tank 48 inches in diameter and 96 inches tall holds roughly 940 US gallons. All dimensions must be converted to inches before dividing by 231 for US gallons or 277.4194 for UK imperial gallons.
What is the formula for cylinder volume in gallons?
The formula for cylinder volume in US liquid gallons is V = (π × r² × h) ÷ 231, where r is the radius in inches, h is the height in inches, and 231 is the exact number of cubic inches per US liquid gallon. For UK imperial gallons, replace 231 with 277.4194. Both divisors derive from internationally recognized gallon definitions used in metrology and engineering, including standards referenced by NIST for volumetric calibration.
What is the difference between US and UK gallons in cylinder volume calculations?
A US liquid gallon equals exactly 231 cubic inches, while a UK imperial gallon equals 277.4194 cubic inches — approximately 20% larger. For a cylinder 24 inches in diameter and 48 inches tall, the US gallon result is approximately 94.0 gallons, while the UK imperial result is only about 78.3 gallons. Selecting the wrong gallon type introduces a nearly one-fifth measurement error, which is significant for chemical dosing, storage planning, or regulatory compliance calculations.
How do I calculate the volume of a horizontal cylindrical tank in gallons?
For a completely full horizontal cylinder, the volume formula is identical to a vertical one: V = (π × r² × L) ÷ 231, where L is the total horizontal length in inches and r is the interior radius in inches. A horizontal propane tank measuring 30 inches in diameter and 72 inches long holds (π × 15² × 72) ÷ 231 = approximately 220.3 US gallons when completely full. Partial-fill calculations for horizontal tanks require a separate circular segment area formula.
What size cylinder holds 100 US gallons?
To contain exactly 100 US gallons, a cylinder must enclose 23,100 cubic inches (100 × 231). For a 24-inch inside diameter tank with a 12-inch radius, solving π × 144 × h = 23,100 gives a required height of approximately 51.1 inches. An 18-inch diameter cylinder would need roughly 90.9 inches — about 7.6 feet — of height to reach 100 gallons. Increasing the diameter proportionally reduces the required height for the same target volume.
How accurate is the cylinder volume gallons calculator for manufactured tanks?
The formula V = (π × r² × h) ÷ 231 assumes a perfect right circular cylinder with a uniform diameter from base to top. For standard manufactured tanks — steel, polyethylene, or fiberglass — accuracy is typically within ±1% of actual rated capacity. Irregularities such as tapered walls, domed or conical ends, or internal fittings reduce precision. For regulatory compliance or legally certified capacity figures on specialty vessels, always consult the manufacturer's stamped capacity plate or a certified capacity chart.