Cubic Feet Cylinder Calculator - Volume in Cubic Feet, Gallons, and Liters
Use this cubic feet cylinder calculator to compute the volume of a right circular cylinder in cubic feet, plus gallons, liters, cubic inches, and cubic meters.
Cubic Feet Cylinder Calculator
Results
What Is Cubic Feet Cylinder Calculator?
A cubic feet cylinder calculator is a focused geometry tool that converts the radius or diameter and height of a right circular cylinder into volume expressed in cubic feet, alongside equivalent values in cubic inches, cubic meters, liters, and US gallons. It is built for situations where the answer must come out in feet - such as ordering a propane tank, sizing a cylindrical water heater, or estimating the capacity of a vertical storage silo - and the linear dimensions are read from a tape measure, blueprint, or product spec sheet.
- • Residential Cylindrical Tanks: Estimate propane, water, or fuel tank capacity in cubic feet and US gallons from the tank diameter and height stamped on the nameplate.
- • Vertical Storage Silos and Barrels: Compute the interior volume of a vertical silo, rain barrel, or steel drum when only the inner diameter and height are available.
- • Plumbing Pipe and Duct Volume: Find the internal volume of a pipe or HVAC duct run by treating it as a long cylinder with the measured inside diameter and total length.
- • Soil Core and Concrete Column Samples: Convert the dimensions of a cylindrical soil sample or concrete test cylinder into cubic feet for density and compressive-strength reporting.
Many product spec sheets list dimensions in inches while capacity is quoted in gallons or liters, which forces a two-step conversion. The cubic feet cylinder calculator keeps the inputs in whatever unit you measured in - inches, feet, centimeters, or meters - and produces the cubic feet answer in a single pass.
For a more general cylinder tool that does not anchor on cubic feet, see our cylinder volume calculator, which lists the same formula in a more abstract form.
How Cubic Feet Cylinder Calculator Works
The cubic feet cylinder calculator squares the base radius, multiplies by the height, and applies pi to find the geometric volume in the selected linear unit. The result is converted to cubic feet using NIST-anchored unit ratios so cubic feet is always the primary answer, with cubic inches, cubic meters, liters, and US gallons listed as secondary conversions.
- r (radius): Distance from the center of the circular base to its edge, expressed in the chosen unit. Enter d/2 manually or select Diameter to have the calculator halve it for you.
- d (diameter): Full width of the circular base through the center. Choose Diameter mode so the calculator uses d/2 as the radius.
- h (height): Perpendicular height of the cylinder along its central axis, in the same unit as r or d.
- pi: Mathematical constant approximately equal to 3.14159265359, applied to convert the circular base area into a volume.
The conversion from cubic feet to the secondary units uses 1 ft^3 = 1728 in^3, 1 ft^3 = 0.028316846592 m^3, 1 ft^3 = 28.316846592 L, and 1 ft^3 = 7.48051948 US gal. These ratios come from the NIST definition of the foot, so the cubic feet primary output and every secondary value are traceable to a single source.
When you change the linear unit selector, the calculator rescales the base and height to feet before applying the formula. The cubic feet value stays consistent across units, while the secondary outputs simply reflect the larger or smaller underlying cylinder.
Worked Example: 6 inch radius by 12 inch height
inputMode = radius, dimension = 6 in, height = 12 in, unit = in
1. Convert to feet: r = 6 in / 12 = 0.5 ft, h = 12 in / 12 = 1 ft. 2. Apply V = pi * r^2 * h = pi * (0.5)^2 * 1 = pi * 0.25. 3. pi * 0.25 = 0.7854 ft^3. 4. Convert to other units: 0.7854 ft^3 * 1728 = 1357.17 in^3, * 28.3168 = 22.24 L, * 7.48052 = 5.88 US gal.
0.7854 ft^3 (about 5.88 US gallons)
A 6 inch radius by 12 inch tall cylinder holds roughly 5.88 US gallons of liquid, useful when sizing a small homebrew keg or a sample test cylinder.
According to Wolfram MathWorld, the volume of a right circular cylinder of radius r and height h is V = pi * r^2 * h.
If you only need to convert a finished cubic feet value into cubic meters, the cubic feet to cubic meters calculator handles that conversion without re-entering the radius and height.
Key Concepts Explained
Four ideas keep the math grounded: the geometric formula itself, the unit ratios that power the conversions, the difference between radius and diameter, and the connection between cubic feet and US gallons for liquid capacity.
Right Circular Cylinder
A solid with two parallel circular bases of the same size joined by a curved side, where the height runs perpendicular to the bases. This is the standard shape assumed by V = pi r^2 h.
Cubic Foot (ft^3)
The volume of a cube with sides of one foot. 1 ft^3 equals 1728 in^3, 0.0283168 m^3, 28.3168 L, and 7.48052 US liquid gallons.
Radius vs Diameter
The radius is half the diameter. If the measured value is the full width across the circular face, pick Diameter mode so the calculator halves it before squaring.
Cubic Feet to Gallons
Capacity in US gallons is 7.48052 times the cubic feet value. Use this when a tank is sold by the gallon but only measured in feet.
When the cylinder is hollow, like a pipe wall, the inner radius and outer radius produce different volumes. Treat the wall as a separate outer cylinder and subtract the inner cylinder's volume for the material volume of the pipe itself.
If you need to go the other direction - turn a gallon rating back into cubic feet - the gallons to cubic feet calculator walks through the inverse conversion without re-entering the radius and height.
How to Use This Calculator
Enter the base dimension, height, and unit, and the calculator updates every output the moment any field changes.
- 1 Pick Radius or Diameter: Use the Base Input selector to tell the calculator whether the value you are about to type is the radius (half the width) or the full diameter of the circular base.
- 2 Enter the Base Dimension: Type the measured radius or diameter in the numeric field. Inches are the most common default for small cylinders, but any of the four units work.
- 3 Enter the Cylinder Height: Provide the perpendicular height of the cylinder in the same unit. For a horizontal pipe run, the height is the length of the pipe.
- 4 Choose the Linear Unit: Select inches, feet, centimeters, or meters so the calculator can convert both base and height to feet before applying the formula.
- 5 Read the Outputs: Read the primary cubic feet value, then scan the secondary row for cubic inches, cubic meters, liters, and US gallons when you need them.
For a residential propane tank that is 1.5 ft in radius and 4 ft tall: the user picks Radius, enters 1.5 in the base field, enters 4 in the height field, and leaves the unit selector on Feet. The calculator shows about 28.27 ft^3, which converts to roughly 211.5 US gallons of usable capacity.
For tanks that are partly full, lay on their side, or use a non-cylindrical shape, switch to the tank volume calculator, which supports those layout-specific cases.
Benefits of Using This Calculator
The biggest advantage of a dedicated cubic feet cylinder tool is that the primary unit, the conversion ratios, and the geometric formula all live in one place.
- • Anchored to Cubic Feet: The primary output is always cubic feet, the unit used in HVAC manuals, propane tank spec sheets, and US building codes for room volume.
- • Pick the Unit You Measured In: The shared linear unit selector accepts inches, feet, centimeters, or meters for both the base dimension and the height, so a nameplate in inches and a spec sheet in centimeters do not need to be reconciled by hand.
- • Full Capacity in One View: See cubic feet, gallons, liters, cubic inches, and cubic meters at the same time, so capacity quotes from different suppliers can be compared directly.
- • Avoids Pi Mistakes: The math engine uses the full double-precision value of pi, eliminating the rounding error that creeps in when pi is typed by hand as 3.14.
- • Tape-Measure Friendly: Inputs accept decimals, so a 17 3/4 inch diameter can be entered as 17.75 without first converting it to a fraction.
If the project has shifted from a tank to a flat rectangular storage area, a cubic feet calculator is the better fit because it works on length, width, and height rather than radius and height.
Factors That Affect Your Results
Three variables drive how much the actual volume can differ from the geometric answer: which diameter you measured, which unit the spec sheet is in, and whether the cylinder is hollow.
Inner vs Outer Diameter
For pipes and tanks with thick walls, the inner diameter gives the capacity for liquid or gas, while the outer diameter includes the wall material. Measure the inside of the opening for capacity questions.
Unit Inconsistency
A common error is to enter the radius in inches and the height in feet. The calculator will still produce a number, but it will mix the two units. Pick a single unit and convert the other dimension before typing it in.
Hollow Cylinders
Treating a pipe as a solid cylinder overstates the liquid volume by including the wall material. Compute the outer cylinder and subtract the inner cylinder for the wall volume, or use a pipe-specific tool.
- • The calculator assumes a right circular cylinder with flat, parallel bases. Tapered tanks, domed ends, and horizontal cylinders require different formulas.
- • The output is a geometric volume, not a wet volume. The calculator does not account for headspace, fill levels, fittings, or thermal expansion of the contents.
The conversion factors that take cubic feet into cubic inches, cubic meters, liters, and US gallons come from the NIST definition of the foot, so the secondary values stay accurate across any size of cylinder. Pi itself is a mathematical constant and does not vary with the cylinder, but if the working temperature is far from 20 degrees Celsius, the linear dimensions can shift slightly; for everyday tape-measure work the geometric value is well within the tolerance of the measurement.
According to National Institute of Standards and Technology (NIST), the foot is defined as exactly 0.3048 meters, which fixes 1 cubic foot at 0.028316846592 cubic meters and 28.316846592 liters.
For very long pipe networks, a pipe volume calculator batches the result across many segments and handles the hollow-pipe math for you.
Frequently Asked Questions
Q: How do you calculate cubic feet of a cylinder?
A: Square the radius of the circular base, multiply by the perpendicular height, and multiply by pi (3.14159...). If the diameter is supplied, halve it first to get the radius. Convert the answer from the input unit to feet before reading the cubic feet value.
Q: What is the formula for the volume of a cylinder in cubic feet?
A: V (ft^3) = pi * r (ft)^2 * h (ft). When the dimensions are measured in inches, centimeters, or meters, convert them to feet first, then apply the same formula.
Q: How many cubic feet are in a cylinder?
A: It depends entirely on the radius and height. A 1 foot radius by 1 foot tall cylinder is about 3.1416 ft^3, while a 2 foot radius by 4 foot tall cylinder is about 50.27 ft^3.
Q: How do I find the radius of a cylinder in feet?
A: Measure the diameter across the circular face and divide by two. If the measurement is in inches, divide by 12 as well to convert to feet. The calculator can do the division for you when you select Diameter mode.
Q: How do I convert cylinder volume to gallons?
A: Multiply the cubic feet value by 7.48052. For example, 10 ft^3 is 74.81 US gallons. The calculator shows the gallons value directly so no extra conversion is needed.
Q: What units does the cubic feet cylinder calculator support?
A: The base dimension and height can be entered in inches, feet, centimeters, or meters. The outputs always include cubic feet, cubic inches, cubic meters, liters, and US gallons regardless of which input unit is chosen.