Concrete Pier and Form Tube Calculator
Enter a form tube or pier diameter and depth, add a bell if there is one, and get the bags for each pier and for all of them, with the working shown. Add piers with the copies control. Volume only.
A ready-made setup of the Concrete Calculator.
Estimates for planning, not professional advice. Read the full notice.
Example: one form tube pier
6 80 lb bags
- Concrete in the pier 3.14 ft³
- To mix, with waste 3.46 ft³
Estimate for planning, from what you entered and the product data shown. Check product labels and your supplier before you buy.
Your project
Enter a size to see your total.
Each product is rounded up once for the whole project, so the total can be less than the items bought alone added together. A line counted from a cut layout (sheets, boards or tiles laid out piece by piece) is counted for each item and added.
Shopping list
| Item | Size | Buy |
|---|---|---|
| Concrete mix | 80 lb bag | 6 |
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Worked example: one form tube pier
Show the working
Assumptions
The figures behind the example. Sourced figures link to their source below; a default is a starting value to check against your label or supplier.
| Assumption | Value | Details and changes |
|---|---|---|
| Concrete waste allowance | 10%[1] | |
| Default 10% is the top of NRMCA's 4% to 10% range. | ||
| Yield of the 40 lb bag | approx. 0.3 ft³[2] | |
| A 40 lb bag of QUIKRETE Concrete Mix 1101 yields about this many cubic feet, as the maker's own sheet states. | ||
| Yield of the 50 lb bag | approx. 0.375 ft³[2] | |
| A 50 lb bag of QUIKRETE Concrete Mix 1101 yields about this many cubic feet, as the maker's own sheet states. | ||
| Yield of the 60 lb bag | approx. 0.45 ft³[2] | |
| A 60 lb bag of QUIKRETE Concrete Mix 1101 yields about this many cubic feet, as the maker's own sheet states. | ||
| Yield of the 80 lb bag | approx. 0.6 ft³[2] | |
| An 80 lb bag of QUIKRETE Concrete Mix 1101 yields about this many cubic feet, as the maker's own sheet states. | ||
| Yield of the 90 lb bag | approx. 0.675 ft³[2] | |
| A 90 lb bag of QUIKRETE Concrete Mix 1101 yields about this many cubic feet, as the maker's own sheet states. | ||
Feet and inches, like 12' 6"
Concrete in a form tube, by diameter and depth
Concrete in one filled form tube and the 80 lb bags to buy for it, by tube diameter, at two depths, with the waste allowance added
| Tube diameter | Concrete at 3 ft deep | 80 lb bags at 3 ft deep | Concrete at 4 ft deep | 80 lb bags at 4 ft deep |
|---|---|---|---|---|
| 6 in | 0.59 ft³ | 2 × 80 lb bags | 0.79 ft³ | 2 × 80 lb bags |
| 8 in | 1.05 ft³ | 2 × 80 lb bags | 1.4 ft³ | 3 × 80 lb bags |
| 10 in | 1.64 ft³ | 3 × 80 lb bags | 2.18 ft³ | 4 × 80 lb bags |
| 1 ft | 2.36 ft³ | 5 × 80 lb bags | 3.14 ft³ | 6 × 80 lb bags |
Tube diameters are the sizes the form tube maker lists. A bell at the bottom adds its own volume; the calculator takes it as an option. Product names are trademarks of their owners. HoneyDoMath is not affiliated with, sponsored by or endorsed by these makers.
Six piers: mixed across the holes or whole bags per hole
80 lb bags for six 12 in piers, 4 ft deep, counted across all the holes and as whole bags for each hole, with the same waste allowance as the calculator
| Way of buying | 80 lb bags |
|---|---|
| Mixed across the holes | 35 × 80 lb bags |
| Whole bags for each hole | 36 × 80 lb bags |
The calculator's total mixes across the holes, so the bags are rounded up once. Mixing each hole from whole bags can need more.
Questions
How many bags fill a 12 inch form tube?
The table on this page gives the bags for each tube diameter the maker lists, at two depths, with the waste allowance added. Enter your own depth in the calculator for the exact count.
How deep does a pier go?
The calculator takes the depth you enter. The frost line is local, so ask your building department what applies where you build.
Is a bell included?
Only when you switch it on. A bell is the frustum under the shaft; its volume is added once to the shaft and never counted twice.
Sources (3)
-
CIP 31, Ordering Ready Mixed Concrete (opens in new tab), National Ready Mixed Concrete Association, 2000, 2016, 2023.
Standards or industry body.
“Quantity of concrete ordered should be 4% to 10% more than an estimate calculated from the plan dimensions to account for contingencies.”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 1) -
QUIKRETE Concrete Mix No. 1101 data sheet (opens in new tab), The Quikrete Companies, Revised October 2022.
Manufacturer data.
“An 80 lb (36.2 kg) bag yields approximately 0.60 ft3 (17 L)”
“A 40 lb (18.1 kg) bag yields approximately 0.30 ft3 (8.5 L)”
“A 50 lb (22.6 kg) bag yields approximately 0.375 ft3 (10.6 L)”
“A 60 lb (27.2 kg) bag yields approximately 0.45 ft3 (12.7 L)”
“A 90 lb (40.8 kg) bag yields approximately 0.675 ft3 (19.1 L)”
Per QUIKRETE's data sheet, checked Nov 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 2) -
QUIKRETE QUIK-Tubes No. 6922 data sheet (opens in new tab), The Quikrete Companies, Undated data sheet.
Manufacturer data.
“Available in 6" (152 mm), 8" (203 mm), 10" (254 mm) and 12"(305 mm) diameters in 4' (1.2 M), lengths.”
Per QUIKRETE's data sheet, checked Nov 12, 2026. Figures and codes change; verify with the source.
These are summaries of what the sources say, not professional advice. Codes and product data change. Check with your building department and the product label about your own project.
Sources
- [1] National Ready Mixed Concrete Association, CIP 31, Ordering Ready Mixed Concrete. Checked November 12, 2026. https://www.nrmca.org/wp-content/uploads/2021/01/31pr.pdf
- [2] QUIKRETE, QUIKRETE Concrete Mix No. 1101 data sheet. Checked November 12, 2026. https://www.quikrete.com/PDFs/DATA_SHEET-Concrete%20Mix%201101.pdf
- [3] QUIKRETE, QUIKRETE QUIK-Tubes No. 6922 data sheet. Checked November 12, 2026. https://www.quikrete.com/pdfs/data_sheet-quiktube.pdf