Column Volume Calculator
A column is a cylinder standing on end, and its volume answers two different shopping questions. If the column is a tank, silo or post hole, you want to know how much liquid or fill it holds. If you are pouring it, you want an order quantity: cubic yards for ready-mix, or a bag count you can load at the store.
The calculator below handles both jobs in one card. The Cylinder volume tab reports gallons, cubic feet, cubic inches, liters and cubic meters from any diameter and height. The Concrete columns tab takes round, square or rectangular columns, a count and a waste allowance, and returns the order volume, both standard bag counts and an optional material cost.
Quick Answer
Key takeaways
- Volume is base area times height: pi x r2 x h for a round column. Always halve the diameter first; squaring the full diameter overstates the volume four times over.
- Bag counts use the manufacturer yields: about 0.6 ft3 per 80 lb bag and 0.45 ft3 per 60 lb bag, always rounded up.
- Waste is applied before the bag count, not after: order volume = total volume x (1 + waste %).
- Units can mix freely. A diameter in inches with a height in feet is converted internally, which is how most people actually measure.
- Quick Answer
- How to use the two tabs
- The formulas behind both tabs
- Worked examples, checked against the tool
- Bags or ready-mix: where the crossover sits
- Wet volume, dry volume, and the 1.5x figure you may have heard
- What this calculator covers, and why each part matters
- Frequently Asked Questions
- Add This Calculator to Your Website
- References
How to use the two tabs
Start on the tab that matches your question. If something goes into the column (water, grain, soil, air), stay on Cylinder volume. If the column is concrete, switch to Concrete columns.
Measure the diameter, not the radius. Both tabs ask for the full width, because that is what a tape measure gives you. The halving happens inside the formula.
Set each unit separately. Diameter in inches and height in feet is the normal jobsite combination, and the converter handles it. There is no need to pre-convert anything to a single unit system.
On the concrete tab, add count and waste. Enter how many identical columns you are pouring and keep the waste allowance at 10% unless your forms are unusually true and the pour is easy to top up.
Add a bag price only if you want the cost line. The material cost uses the 80 lb bag count. Leave the price at 0 and the cost row simply does not appear.
The formulas behind both tabs
A cylinder’s volume is the area of its circular base multiplied by its height, the same base-times-height rule the BYU-Idaho geometry course notes use for right circular cylinders. Square and rectangular columns swap the circle for their own base area.
The bag yields are the manufacturers’ published figures for standard concrete mix (QUIKRETE technical data lists about 0.60 ft3 per 80 lb bag and 0.45 ft3 per 60 lb bag), and they already account for the water added at mixing. That is why no separate dry-volume factor appears anywhere in the concrete tab: bagged mix is sold by its wet, in-place yield.
Worked examples, checked against the tool
| Example | Inputs | Result |
|---|---|---|
| Tank volume | Diameter 24 in, height 10 ft | 235.01 gallons (31.42 ft3, 54,287 in3, 889.6 L, 0.890 m3) |
| One concrete column | Round, 12 in diameter, 8 ft tall | 6.28 ft3 |
| Four columns, no waste | As above, count 4 | 25.13 ft3 |
| Order quantity | As above, 10% waste | 27.65 ft3 = 1.02 yd3 |
| Bags | 27.65 ft3 order volume | 47 x 80 lb bags or 62 x 60 lb bags |
| Material cost | 47 bags at $5.50 entered as bag price | $258.50 |
Check the tank by hand: the radius is 1 foot, so V = 3.1416 x 1 x 10 = 31.42 ft3, and 31.42 x 7.48052 = 235.01 gallons. Check the columns the same way: one column is pi x 0.52 x 8 = 6.28 ft3; four make 25.13 ft3; adding 10% gives 27.65 ft3, and 27.65 / 0.6 = 46.1, which rounds up to 47 bags. The cost row only appears when you enter a price: at $5.50 a bag, 47 bags come to $258.50. For pours that are not columns at all, slabs, footings and walls, the general concrete volume calculator covers those shapes, and the cement cost per cubic yard calculator prices ready-mix by the yard once a job outgrows bags.
Bags or ready-mix: where the crossover sits
The worked example sits right at the decision point. Forty-seven 80 lb bags weigh 3,760 lb before water, and every one of them has to be lifted, opened, mixed and placed inside the working time of the batch before it. A ready-mix truck delivers the same 1.02 cubic yards in one pour, usually with a minimum load or short-load fee that punishes small orders.
As a working rule: under about half a yard, bags win on simplicity. Between half a yard and a yard and a half, compare the bag total (with an honest price per bag) against the delivered ready-mix quote including short-load fees. Past roughly two yards, hand-mixing stops being a plan and becomes an endurance event, and the truck wins almost every time. The weight figure explains why: concrete runs about 150 lb per cubic foot, so a cubic yard is roughly 4,050 lb of material however it arrives. Round columns poured in tube forms have their own close cousin in this batch: the circle volume calculator covers the circular base geometry on its own.
Wet volume, dry volume, and the 1.5x figure you may have heard
Wet volume is the concrete that ends up in the forms, and it is the only volume bag counts care about. Dry volume is the loose cement, sand and aggregate before water and compaction, roughly 1.5 times the wet volume, and it matters only when you are batching raw materials yourself by volume. If you are buying bagged mix, the yield printed on the bag is already a wet, in-place figure, so applying a dry-volume factor on top double-counts and over-orders by half. Several older guides blur this distinction; this calculator does not, and the FAQ below states it plainly.
What this calculator covers, and why each part matters
This calculator does two jobs on one page, with the arithmetic visible at every step: the volume of a round column or tank, and the concrete order for a set of columns.
- Volume in five units. Volume is base area times height: pi × r² × h for a round column. Always halve the diameter first; squaring the full diameter overstates the volume four times over. A cylinder 24 inches across and 10 feet tall holds 31.42 ft³, which is 235.01 US gallons (889.6 liters). Units can mix freely: a diameter in inches with a height in feet is converted internally, which is how most people actually measure.
- Concrete from the same page. Four round concrete columns 12 inches in diameter and 8 feet tall, with 10% waste, need 1.02 cubic yards of concrete: 47 bags of 80 lb mix or 62 bags of 60 lb mix.
- Waste applied before the bag count, not after. Order volume = total volume × (1 + waste %). Bag counts use the manufacturer yields – about 0.6 ft³ per 80 lb bag and 0.45 ft³ per 60 lb bag – always rounded up, so the order never comes up short.
- Every number checkable against the line above it. On the concrete side, the per-column figure, the total, the waste-adjusted order, both bag sizes and an optional cost appear in that order, so each result can be checked against the line above it.
Frequently Asked Questions
Find the column’s volume in cubic feet, multiply by the number of columns, add your waste allowance, then divide by 0.6 for 80 lb bags or 0.45 for 60 lb bags and round up. A 12 inch round column 8 feet tall is 6.28 ft3, so one column with 10% waste needs 12 bags of 80 lb mix.
Use 10% for site-mixed or hand-placed pours and anything with imperfect formwork. Five percent is defensible for straight, well-braced forms filled by ready-mix. When a pour cannot easily be topped up, round up rather than down: a spare bag is cheaper than a short column.
Wet volume is the concrete in the forms. Dry volume is the loose material before mixing, roughly 1.5 times the wet volume, and it is used when batching cement, sand and aggregate yourself. Bagged mix yields are wet figures already, so the bag count here needs no dry-volume factor.
Yes. Every dimension has its own unit selector and everything converts internally, so a 24 inch diameter with a 10 foot height gives exactly the worked-example result of 235.01 gallons.
About 150 lb per cubic foot, so a full cubic yard weighs roughly 4,050 lb. That weight is why ready-mix delivery becomes the sensible choice once a job passes a couple of cubic yards.
About 45. One cubic yard is 27 ft3 and an 80 lb bag yields about 0.6 ft3, so 27 / 0.6 = 45 bags. For 60 lb bags at 0.45 ft3 each, the figure is 60 bags per yard.
Yes. On the Concrete columns tab, choose Square and enter the side length, or Rectangular and enter width and depth. The volume formula changes to side squared x height or width x depth x height, and the count, waste, bag and cost steps work the same way.
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References
- Brigham Young University-Idaho, geometry course notes on the volume of a right circular cylinder: V = pi x r2 x h from the circular base area times the height. BYU-Idaho: Volume of a Right Circular Cylinder. Accessed October 2026.
- QUIKRETE Companies, Concrete Mix technical data: published mixed yields of about 0.60 ft3 per 80 lb bag and 0.45 ft3 per 60 lb bag, the yields used for the bag counts on this page. Manufacturer technical data sheet, consulted October 2026.
- Constropedia, guide to calculating concrete volume for construction projects, including circular columns worked step by step. Constropedia: How to Accurately Calculate Concrete Volume. Accessed October 2026.