Concrete column and Sonotube calculator

Four round piers 12 in across and 4 ft deep hold 12.57 cu ft (0.47 cubic yards) of concrete. With 10% extra that is 24 bags of 80 lb mix.

Diameter

Height or depth

Number of columns

Extra for waste

0.51 cubic yards

24 80 lb bags

31 60 lb bags

Each column	3.14 cu ft (6 bags of 80 lb)
Volume	12.57 cu ft (0.47 cu yd, 0.356 m³)
With 10% extra	13.82 cu ft (0.51 cu yd)
Ready-mix to order	0.75 cu yd (rounded up to the next ¼ yard)
40 lb bags	47 (0.3 cu ft each)
50 lb bags	37 (0.375 cu ft each)
60 lb bags	31 (0.45 cu ft each)
80 lb bags	24 (0.6 cu ft each)
90 lb bags	21 (0.675 cu ft each)
Weight of the concrete	about 2,004 lb (1.00 tons)

How it was worked out

π × (12 in ÷ 2)² × 4 ft × 4 = 12.57 cu ft

12.57 cu ft ÷ 27 = 0.47 cu yd

How it works

A round column is a cylinder: π × radius² × height. Enter the diameter of the hole or form tube and its height, and the number of identical columns. For a pier poured into a tube that sits in a hole, measure the tube's full length, including the part below ground.

π × (12 in ÷ 2)² × 4 ft × 4 = 12.57 cu ft

12.57 cu ft ÷ 27 = 0.47 cu yd

With 10% extra: 0.51 cu yd, or 24 bags of 80 lb mix

Concrete per foot of form tube

Multiply the figure for your tube size by its length in feet. The bag counts are per foot, so round up only once you have the total.

Round forms, no extra included
Tube diameter	Cu ft per ft	80 lb bags per ft	60 lb bags per ft	Cu yd per 10 ft
6 in	0.196	0.33	0.44	0.07
8 in	0.349	0.58	0.78	0.13
10 in	0.545	0.91	1.21	0.20
12 in	0.785	1.31	1.75	0.29
14 in	1.069	1.78	2.38	0.40
16 in	1.396	2.33	3.1	0.52
18 in	1.767	2.95	3.93	0.65
20 in	2.182	3.64	4.85	0.81
24 in	3.142	5.24	6.98	1.16

Deck and porch piers, 4 ft deep

One pier 4 ft long, with 10% extra
Diameter	Cu ft per pier	80 lb bags per pier	60 lb bags per pier
8 in	1.4	3	4
10 in	2.18	4	6
12 in	3.14	6	8
14 in	4.28	8	11
16 in	5.59	11	14

Piers that hold up a structure must reach below the local frost line. QUIKRETE's post-setting guide says a structural post hole must extend at least 6 in below it. Your building department can tell you the frost depth and the pier size your deck needs.

Sources

QUIKRETE Concrete Mix (No. 1101) data sheet, The QUIKRETE Companies, revised October 2022. Bag yields: 40 lb 0.30 cu ft, 50 lb 0.375, 60 lb 0.45, 80 lb 0.60, 90 lb 0.675; about 140 lb per cubic foot.
Setting Posts (project sheet), The QUIKRETE Companies, current sheet. Hole 3 times the post diameter; depth one third of the post length plus 6 in of gravel; concrete to 3 to 4 in below the top; 6 in below the frost line for structural posts.
CIP 8: Discrepancies in Yield (Concrete in Practice series), National Ready Mixed Concrete Association, 2016 edition. Order at least 4 to 10 percent more than the measured volume; 1/8 in extra on a 4 in slab is a 3 percent shortfall.