RC Reminder Calculator

Cylinder Volume in Gallons

This calculator converts cylinder volume directly into gallons. Enter radius and height in your preferred unit, and the tool outputs the result in both US gallons and Imperial gallons. One US gallon = 3,785.41 cm³; one Imperial gallon = 4,546.09 cm³.

Volume in Gallons Calculator

V = πr²h × 0.000264172
Volume → Gallons × 0.000264 cm³ to US gallons

US Gallons vs Imperial Gallons

A ⟷ B US 3.785L vs UK 4.546L

The US gallon (3.785 litres) and the Imperial gallon (4.546 litres) are different. The US gallon is used in the United States, while the Imperial gallon is used in the UK and some Commonwealth countries.

When converting cylinder volume, always specify which gallon you mean. A 50-litre cylinder holds 13.21 US gallons but only 11.00 Imperial gallons. The difference is about 20%, which matters for fuel tanks, pools, and large containers.

How to Convert Cylinder Volume to Gallons

V(cm³) × 0.000264 = gal

Calculate volume in cubic inches using V = π × r² × h (with inches). Then divide by 231 for US gallons, or divide by 277.42 for Imperial gallons.

Alternatively, calculate in cm³ first, then divide by 3,785.41 (US) or 4,546.09 (Imperial).

Example: A cylindrical drum with radius 11.5 inches and height 33.5 inches has V = π × 132.25 × 33.5 = 13,917.9 in³. That's 60.25 US gallons.

Practical Uses for Gallon Measurements

Fuel • Pool • Tanks

Gallon measurements are standard for fuel tanks, water heaters, swimming pools, and brewing equipment in the US. A typical home water heater is a 40- or 50-gallon cylinder. A standard oil drum holds 55 US gallons.

For pool owners, knowing the gallon capacity determines chemical dosing. For brewers, fermenter size in gallons dictates batch size. Fuel tank capacity in gallons affects vehicle range and refueling planning.

Frequently Asked Questions

How many gallons does a 55-gallon drum actually hold?
A standard 55-gallon drum has interior dimensions of roughly r = 11.25 in, h = 33.5 in. V = π × 126.56 × 33.5 ≈ 13,317 in³ ÷ 231 = 57.65 US gallons. The '55-gallon' label refers to its nominal capacity.
How do I convert litres to US gallons?
Divide litres by 3.78541. For example, 100 litres = 26.42 US gallons.
How many gallons is a cylinder 4 feet tall and 2 feet wide?
Radius = 12 inches, height = 48 inches. V = π × 144 × 48 = 21,714.7 in³ ÷ 231 = 94.0 US gallons.
Why are US and Imperial gallons different?
They evolved from different historical standards. The US gallon was based on the wine gallon (231 in³), while the Imperial gallon was defined as 10 pounds of water at 62°F (277.42 in³).
How do I find the gallon capacity of a round tank?
Measure the inside diameter and height in inches. Use V = π × (d/2)² × h, then divide by 231 for US gallons. For a tank 24 in wide and 36 in tall: V = π × 144 × 36 = 16,286 in³ = 70.5 US gallons.