Cylinder Volume Calculator — Cubic Feet
Real-time cylinder volume using V = π × r² × h. Toggle between diameter and radius input.
The Formula
V = π × r² × h
π (pi) ≈ 3.14159. If you have diameter instead of radius, divide diameter by 2 to get r.
Applications
Tanks & Drums
Water tanks, fuel tanks, 55-gal drums — all cylinders. Measure diameter and height inside the tank, calculate volume, multiply by 7.48 for gallons.
Concrete Columns & Footings
Sonotube footings: a 12 in diameter × 4 ft tall column = π × 0.5² × 4 = 3.14 ft³ of concrete. For multiple footings, multiply by the count.
Tree Planting Holes
Calculate how much backfill or compost a planting hole needs. A 24-in diameter × 24-in deep hole = π × 1² × 2 = 6.28 ft³.
Pipes & Conduits
Internal pipe volume for flow capacity: use the inside diameter, not outside.
Worked Examples
A 12-in diameter sonotube, 6 ft tall: r = 0.5 ft, V = 3.14159 × 0.25 × 6 = 4.71 ft³ = 0.175 yd³.
A round tank 4 ft diameter × 5 ft tall: r = 2 ft, V = 3.14159 × 4 × 5 = 62.83 ft³ = 470 US gallons.
A grain bin 18 ft diameter × 20 ft tall: r = 9 ft, V = 3.14159 × 81 × 20 = 5,089 ft³.
Cylinder vs Other Shapes
Not every round object is a true cylinder. A shape that tapers to a point — a funnel, a conical gravel pile, a cone-bottomed hopper — needs the cone formula instead, which gives one-third the volume of a cylinder with the same base and height. A dome or a fully round tank uses the sphere formula. See the volume formulas reference for the full set, or convert your cylinder result to gallons on the gallons calculator if you're sizing a tank.
Frequently Asked Questions
What is the formula for cylinder volume?
V = π × r² × h, where r is the radius and h is the height.
How do I find volume from diameter?
Divide the diameter by 2 to get the radius, then use V = π × r² × h.
How many cubic feet is a 55-gallon drum?
About 7.35 cubic feet. A 55-gal drum is roughly 22.5 in tall × 23.25 in diameter.
How do I calculate concrete for a sonotube?
Use V = π × r² × h. A 12-inch diameter sonotube 4 ft tall = π × 0.5² × 4 = 3.14 ft³.
What's the volume of a tree planting hole?
Treat as a cylinder. A 2 ft diameter × 2 ft deep hole = π × 1² × 2 = 6.28 ft³.
How big is a 100-gallon cylindrical tank?
100 US gal = 13.37 ft³. A common size is 24 in diameter × 70 in tall.
What unit should I use for radius?
Any — but convert to feet before calculating, or use the unit selector. Mixed units must all convert to feet.
Is height the same as length for a horizontal cylinder?
Yes. For a tank lying on its side, 'height' in the formula is the cylinder's length.