Barrel Volume and Capacity Calculator

Find the cubic footage and total volume of a barrel and find how many gallons (or liters) are in the barrel.

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How to Find the Volume of a Barrel

A barrel is a round container with a convex shape that is wider in the middle than at the top and the bottom. They are generally made of wooden slats called staves, which are held together with metal hoops.

To find barrel volume, you will need to know its height, radius of the top, radius of the bottom, and radius in the middle.

Barrel Volume Formula

There are several formulas to calculate barrel volume since the specific curvature of the barrel will change is volume. We have found the following formula for barrel volume to be the most accurate for most barrel shapes:

volume = h × π × ((1.25 × r22) + r12) / 3

The volume of a barrel is equal to the height h times π times two times the middle radius r2 squared, plus the top/bottom radius r1 squared, divided by three.

Another commonly used formula is shown here. The difference in this formula is a larger multiple applied to the middle radius.

volume = h × π × ((2 × r22) + r12) / 3

drawing of a barrel showing how to find the height, middle radius, and top/bottom radius

To use this formula, ensure that the height, top radius, bottom radius, and middle radius values are all in the same unit of measure; inches are most commonly used. Barrel volume can be expressed in cubic feet or cubic meters, but in our experience, a barrel’s capacity is expressed in gallons or liters.

If all dimensions used in the formula are in inches, then the total volume measurement will be in cubic inches.

To get the total volume in cubic feet, convert from cubic inches using the formula ft3 = in3 × 0.000578704. Use our cubic inches to cubic feet calculator to convert quickly.

Example: For a 53-gallon whiskey barrel with a height of 36″, a top/bottom diameter of 21″, and a middle diameter of 26″

top/bottom radius = 21 ÷ 2
top/bottom radius = 10.5

middle radius = 26 ÷ 2
middle radius = 13

volume = (h × π × ((1.25 × r22) + r12)) ÷ 3
volume = (36 × π × ((1.25 × 132) + 10.52)) ÷ 3
volume = (36 × π × ((1.25 × 169) + 110.25)) / 3
volume = (36 × π × (211.25 + 110.25)) ÷ 3
volume = (36 × π × 321.5) ÷ 3
volume = 36,360 ÷ 3
volume = 12,120 in3
12,120 in3 = 7.014 ft3

How Many Gallons Are in a Barrel?

The capacity of a barrel is often measured in gallons. To find how many gallons are in the barrel, simply convert the total volume to gallons.

Gallons can be found using the cubic feet to gallons formula:

gallons = ft3 × 7.480507

Barrel Gallons Formula

Thus, the formula to find how many gallons are in a barrel is:

gallons = h × π × ((1.25 × r22) + r12) / 3 × 7.480507

How Many Liters Are in a Barrel?

You can find how many liters are in a barrel just like finding gallons. Use the cubic feet to liters formula:

liters = ft3 × 28.3168

Barrel Liters Formula

Using the liters conversion above, the formula to find how many liters are in a barrel is:

liters = h × π × ((1.25 × r22) + r12) / 3 × 28.3168

Common Barrel Sizes

Barrels come in many shapes and sizes, but there are some standard sizes used in industry. Barrels are generally used to store beverages such as wine, beer, and liqueurs. They are also very commonly used to store oil and chemicals.

The average size of a 53-gallon whiskey barrel is 36″ high with a top and bottom diameter of 21″ and a middle diameter of 26″.

Historically, oil was stored in wooden barrels that held 42 gallons of oil. That is why the modern standard of oil barrel volume used for pricing and tax is 42 gallons.

In modern industry, oil and chemicals are stored in metal drums, which are far more durable. Oil drums hold 55 gallons of fluid.

Finding barrel volume is relevant when measuring the amount of beverage it contains, which is useful for beer-making, wine-making, and measuring other beverages.

Try our volume calculator to find the volume of many other shapes.