Key numbers
- Solid: 3.1416 × (D ÷ 2)² × H, all in feet
- Hollow: 0.7854 × (outer² − inner²) × H; the core is subtracted
- 10 ft round pad, 4 in: 26.18 ft³ = 0.97 yd³ = 44 × 80 lb bags (48 with 10% extra)
- Ring 36 in outside, 3 in wall: 2.16 ft³ per foot of height, about 324 lb per foot
- Round column or pier? Use the Sonotube calculator, which has the tube sizes
On this page
- How to use the Concrete Cylinder Calculator
- How do you calculate the volume of a concrete cylinder?
- How do you calculate a hollow cylinder?
- How much concrete per foot of hollow cylinder? (chart)
- How much concrete for a round pad? (table)
- How much concrete for a round tank wall?
- How much does a concrete cylinder weigh?
- Concrete cylinders in metric
- Which calculator should I use for round concrete?
- Common cylinder estimating mistakes
- Frequently asked questions
How to use the Concrete Cylinder Calculator
- 1Choose the shapePick round slab or hollow cylinder. Each shape uses its own volume formula.
- 2Pick your unitsEvery dimension has its own unit menu (in, ft, yd, cm or m); changing one converts that number so the size stays the same. The US / Metric switch sets all fields to feet and inches or meters and centimeters and resets them to typical values.
- 3Enter the dimensionsType the diameter (default feet) or thickness (default inches). Measure the inside of the forms and the depth in several places.
- 4Set waste and quantityUse the waste slider (0 to 20%, default 10%) and allow more on uneven ground. If you have several identical pours, enter how many.
- 5Read the resultsSee the volume in cubic yards, cubic feet and cubic meters, the ready-mix order rounded up to ¼ yard, the number of 90, 80, 60, 50 and 40 lb bags rounded up, and the weight at the density you choose (150, 145 or 140 lb/ft³).
- 6Price it and save itPick a pricing basis (per cubic yard, per cubic meter or per bag of the highlighted size) and enter your local price for a material cost. Use Add to project to total several pours, and Copy link to share the exact result.
Results update as you type. Back to the calculator ↑
How do you calculate the volume of a concrete cylinder?
Find the area of the circle and multiply it by the height (or thickness). The area of a circle is π times the radius squared, and the radius is half the diameter. Work in feet and the answer is in cubic feet; divide by 27 for cubic yards.
Solid cylinder (ft³) = 3.1416 × (diameter ÷ 2)² × height
Hollow cylinder (ft³) = 0.7854 × (outer diameter² − inner diameter²) × height
Cubic yards = ft³ ÷ 27 · 80 lb bags = ft³ ÷ 0.60, rounded up
The calculator has two modes. Round slab takes a diameter and a thickness, for patios, pads under tanks, and the bases of round structures. Hollow cylinder takes an outer diameter, an inner diameter, a height and a count, for rings, pipe sections, manhole-style risers and tank walls. Every field accepts inches, feet, yards, centimetres or metres.
Worked example: 10 ft round pad, 4 in thick
- Radius: 10 ÷ 2 = 5 ft; thickness: 4 ÷ 12 = 0.333 ft
- Volume: 3.1416 × 5 × 5 × 0.333 = 26.18 ft³ (0.97 yd³, 0.74 m³)
- With 10% extra: 28.8 ft³ = 1.07 yd³ (0.815 m³)
- 80 lb bags: 28.8 ÷ 0.6 = 48 bags; or 64 bags of 60 lb
- Weight at 150 lb/ft³: about 3,927 lb before the extra
At just over a yard, this is a job to price as ready-mix as well as bags.
How do you calculate a hollow cylinder?
Work out the solid cylinder from the outer diameter, then subtract the empty core from the inner diameter. What is left is the concrete in the wall.
Worked example: ring 36 in outside, 30 in inside, 4 ft tall
- Solid 36 in (3 ft) cylinder: 3.1416 × 1.5² × 4 = 28.27 ft³
- Core, 30 in (2.5 ft): 3.1416 × 1.25² × 4 = 19.63 ft³
- Concrete: 28.27 − 19.63 = 8.64 ft³ (0.32 yd³, 0.245 m³)
- With 10% extra: 9.5 ft³ (0.35 yd³): 16 bags of 80 lb, or 22 of 60 lb
- Weight at 150 lb/ft³: about 1,296 lb
The wall is only 3 in thick, yet the ring holds 31% of the concrete of a solid 36 in cylinder. Thin walls on large diameters add up.
If the inner diameter is equal to or larger than the outer one, the calculator returns zero: check that the two fields are not swapped. Wall thickness is (outer − inner) ÷ 2, so a 36 in ring with a 3 in wall has a 30 in inside diameter.
How much concrete per foot of hollow cylinder? (chart)
Concrete in one foot of height for common outer diameters and wall thicknesses. Multiply by your height or length and the number of pieces.
| Outer diameter (in) | Wall (in) | Inner diameter (in) | ft³ per ft | 80 lb bags per ft | Weight per ft (lb) | Litres per metre |
|---|---|---|---|---|---|---|
| 24 | 3 | 18 | 1.374 | 2.29 | 206 | 127.7 |
| 36 | 3 | 30 | 2.160 | 3.60 | 324 | 200.7 |
| 36 | 4 | 28 | 2.793 | 4.65 | 419 | 259.4 |
| 48 | 4 | 40 | 3.840 | 6.40 | 576 | 356.7 |
| 48 | 6 | 36 | 5.498 | 9.16 | 825 | 510.8 |
| 60 | 6 | 48 | 7.069 | 11.78 | 1,060 | 656.7 |
| 72 | 6 | 60 | 8.639 | 14.40 | 1,296 | 802.6 |
| 120 | 8 | 104 | 19.548 | 32.58 | 2,932 | 1,816.0 |
These are geometry for the sizes you enter, not product dimensions. Precast pipe, manhole sections and culverts are made to their own standards with their own wall thicknesses, so take sizes from the product data or your plans. Weights use 150 lb/ft³ (WSDOT Bridge Design Memo 05-2010; FHWA gives about 140–155 lb/ft³). Bag counts use QUIKRETE’s 0.60 ft³ per 80 lb bag.
How much concrete for a round pad? (table)
Round slabs at the two most common thicknesses, with no extra. Add 5–10% when you order.
| Diameter (ft) | Area (m²) | 4 in: ft³ | 4 in: yd³ | 4 in: 80 lb bags | 6 in: ft³ | 6 in: yd³ | 6 in: 80 lb bags |
|---|---|---|---|---|---|---|---|
| 4 | 1.17 | 4.19 | 0.16 | 7 | 6.28 | 0.23 | 11 |
| 6 | 2.63 | 9.42 | 0.35 | 16 | 14.14 | 0.52 | 24 |
| 8 | 4.67 | 16.76 | 0.62 | 28 | 25.13 | 0.93 | 42 |
| 10 | 7.30 | 26.18 | 0.97 | 44 | 39.27 | 1.45 | 66 |
| 12 | 10.51 | 37.70 | 1.40 | 63 | 56.55 | 2.09 | 95 |
| 14 | 14.30 | 51.31 | 1.90 | 86 | 76.97 | 2.85 | 129 |
| 16 | 18.68 | 67.02 | 2.48 | 112 | 100.53 | 3.72 | 168 |
| 20 | 29.19 | 104.72 | 3.88 | 175 | 157.08 | 5.82 | 262 |
Doubling the diameter quadruples the concrete: a 20 ft pad holds four times a 10 ft pad at the same thickness. For a square or rectangular slab, use the concrete slab calculator.
How much concrete for a round tank wall?
Treat the wall as one hollow cylinder: the outer diameter is the inside diameter plus two wall thicknesses.
Worked example: tank 10 ft inside, 8 in wall, 6 ft tall
- Outer diameter: 10 ft + 2 × 8 in = 11.33 ft
- Wall concrete: 0.7854 × (11.33² − 10²) × 6 = 134.04 ft³ (4.96 yd³, 3.80 m³)
- With 10% extra: 5.46 yd³ (4.18 m³)
- Weight at 150 lb/ft³: about 20,100 lb
Add the floor as a round slab (outer diameter × floor thickness) and any footing separately.
A tank, cistern or wall that holds water or soil is a structural job. Wall thickness, reinforcement and joints come from an engineer or approved plans. This page measures the concrete only.
How much does a concrete cylinder weigh?
Multiply the volume by the density. This site uses 150 lb/ft³ for normal-weight concrete, from WSDOT’s Bridge Design Memo 05-2010; FHWA’s guidance gives a range of about 140–155 lb/ft³, and QUIKRETE lists about 140 lb/ft³ for its bagged Concrete Mix.
| Piece | Volume (ft³) | Weight at 150 lb/ft³ | Weight in kg |
|---|---|---|---|
| Ring 36 in / 30 in × 4 ft | 8.64 | 1,296 lb | 588 kg |
| Round pad 10 ft × 4 in | 26.18 | 3,927 lb | 1,781 kg |
| Tank wall 10 ft inside, 8 in wall × 6 ft | 134.04 | 20,106 lb | 9,120 kg |
Weight matters when a ring or pipe section is cast on the ground and has to be lifted into place later. A 4 ft ring at 1,296 lb is equipment work, not a two-person carry. For other shapes, the concrete weight calculator does the same multiplication.
Concrete cylinders in metric
Use the same formulas with metres. For a hollow cylinder, 0.7854 × (outer² − inner²) × height gives m³ directly.
Worked example: ring 1.2 m outside, 1.0 m inside, 1 m tall
- Volume: 0.7854 × (1.44 − 1.00) × 1 = 0.3456 m³ (346 litres)
- With 10% extra: 0.38 m³ (0.50 yd³)
- 80 lb (36.3 kg) bags: 23
A 3 m round pad 100 mm thick is 3.1416 × 1.5² × 0.1 = 0.71 m³. 1 m³ = 35.3147 ft³ and 1 yd³ = 0.7645549 m³ (NIST SP 811).
Which calculator should I use for round concrete?
Pick by the shape, not by the word “round”:
| Your pour | Use |
|---|---|
| Round patio, pad or slab | This page, Round slab mode |
| Ring, pipe section, riser, tank wall | This page, Hollow cylinder mode |
| Round column or pier formed with a tube | Sonotube calculator |
| Post set in a round hole | Fence post concrete calculator |
| Square or rectangular column or beam | Concrete column calculator |
Common cylinder estimating mistakes
- Using the diameter as the radius. π × D² over-orders by four times. Halve the diameter first, or use 0.7854 × D².
- Mixing inches and feet. A 4 in pad is 0.333 ft thick, not 4 ft.
- Forgetting to subtract the core. A ring is far less concrete than a solid cylinder of the same size.
- Swapping outer and inner diameters. The outer is always the larger one.
- No extra. Uneven ground under a pad and form bulges eat 5–10%.
All results are volume estimates for ordering. Structural walls, tanks and pipes follow their engineer’s or manufacturer’s specifications.
FAQ
Frequently asked questions
How do you calculate the volume of a concrete cylinder?
Multiply π (3.1416) by the radius squared and by the height, all in feet. A 10 ft round pad 4 in thick is 3.1416 × 5 × 5 × 0.333 = 26.18 ft³. Divide by 27 for cubic yards: 0.97 yd³.
How do you calculate the volume of a hollow concrete cylinder?
Work out the solid cylinder from the outer diameter, then subtract the core from the inner diameter. A 36 in ring 4 ft tall is 28.27 ft³ solid; the 30 in core is 19.63 ft³; the concrete is 8.64 ft³ (0.32 yd³).
How many bags of concrete for an 8 ft round pad?
An 8 ft circle 4 in thick holds 16.76 ft³ (0.62 yd³): 28 bags of 80 lb concrete, or 31 with 10% extra. At 6 in thick it holds 25.13 ft³ (0.93 yd³), or 42 bags before extra.
How much concrete for a 12 ft round slab?
A 12 ft circle 4 in thick holds 37.70 ft³ (1.40 yd³), or 1.54 yd³ with 10% extra. That is 63 bags of 80 lb concrete before extra, so a ready-mix delivery is usually easier. At 6 in thick it is 2.09 yd³.
How much concrete is in a concrete pipe per foot?
It depends on the outer diameter and wall. A 48 in outside diameter with a 4 in wall (40 in inside) holds 3.84 ft³ per foot, about 576 lb. A 24 in pipe with a 3 in wall holds 1.37 ft³ per foot, about 206 lb.
How much concrete for a round tank wall?
Use the hollow mode with the outside and inside diameters. A tank 10 ft inside with an 8 in wall, 6 ft tall, is 134.04 ft³ (4.96 yd³), or 5.46 yd³ with 10% extra, weighing about 20,100 lb at 150 lb/ft³. Add the floor separately.
How do you calculate a cylinder in metric?
Use the same formula in metres. A ring 1.2 m outside, 1.0 m inside and 1 m tall is 0.7854 × (1.44 − 1.00) × 1 = 0.3456 m³, or 0.38 m³ with 10% extra (0.50 yd³, 23 × 80 lb bags).
What is the difference between this and a Sonotube calculator?
The Sonotube calculator is for round columns and piers formed with cardboard tubes, with standard tube sizes and several tubes at once. This page is for round pads and hollow shapes: rings, pipes and tank walls, where you subtract a core.
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Last reviewed October 10, 2026 by M Bilal. Found an error? Tell us.