How much concrete for a round form?
Round concrete forms are calculated as cylinders. Use inside diameter, height or depth, and count, then convert the total volume to cubic yards or bags.
Diameter has a big effect
Cylinder volume uses radius squared, so a small increase in diameter can noticeably increase concrete quantity. Measure the inside diameter of the form or hole.
Tubes, piers, columns, and holes
Tube forms, piers, columns, and round holes use similar volume math, but their structural requirements can be very different. This page estimates material quantity only.
Before you calculate
- Enter the inside form diameter, not the outside packaging size.
- Measure height or depth consistently for each tube.
- Use the count input when several identical forms are being poured.
Common mistakes
- Estimating round forms as rectangles.
- Mixing inches and feet for diameter and height.
- Forgetting that over-excavation or an uneven bottom can increase concrete demand.
Formula
cubic yards = count * pi * (diameter / 24)^2 * height / 27 * (1 + wastePercent / 100)
Assumptions
- Defaults represent 16 inch round concrete piers.
- Diameter is entered in inches and height or depth is entered in feet.
- This estimates straight cylindrical volume only; bell bottoms, cages, uplift, frost depth, and inspection requirements are separate.
Example
Estimated concrete needed: 0.68 cubic yards
How to use this round concrete calculator
- Count the matching tubes, piers, columns, or round forms in the project.
- Enter the inside diameter in inches, then enter the concrete-filled height or depth in feet.
- Use separate estimates when round forms have different diameters or depths.
- Review cubic feet, cubic yards, 60 lb bags, and 80 lb bags before comparing bagged concrete with ready-mix.
- Confirm form bracing, frost depth, reinforcement, and inspection requirements outside the calculator.
Before you buy materials
- Round the result up to match ready-mix ordering or bag yield increments.
- Confirm form size, bracing, and placement before using the estimate for ordering.
FAQ
What is the example 16 inch round pier concrete cubic-yard result?
Use diameter or radius, height or depth, count, and waste, then calculate the planning result. In the default example, the result is 0.68 cubic yards.
How do I calculate concrete for a sonotube or tube form?
Calculate the cylinder volume from diameter and height, multiply by count, add waste, then convert to cubic yards or bags.
Do I use inside or outside diameter?
Use inside diameter because that is the space the concrete fills.
How do I calculate multiple piers?
Calculate one pier, then multiply by the number of identical piers. Calculate different pier sizes separately.
Does this design a structural pier or column?
No. It estimates concrete quantity only. Structural sizing and reinforcement require qualified guidance.
Related calculators
This calculator is for planning estimates only. Verify final quantities with product labels, project conditions, and a qualified professional when accuracy matters.