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United States

Concrete Column & Post Hole Calculator

Work out the concrete for round columns and tube forms, or for setting fence and deck posts: the calculator takes the post out of the hole volume for you.

What are you pouring?
Round column or tube form
Diameter Height

Tip: you can type feet and inches, like 10' 6".

Use your own prices (optional)

You need

– cu yd

–

Poured, it weighs about – lb.

Premixed bags

Bag Bags To carry Est. cost

Mixing it yourself (1:2:3)

QUIKRETE Portland Cement data sheet: concrete mix 1 part cement, 2 parts All-Purpose Sand, 3 parts All-Purpose Gravel; 5 to 6 bags of 94 lb per yd³. A 94 lb bag is the customary 1 cu ft of cement.

Ready-mix truck

–

If a contractor pours it

How we price

Link to this calculation Download estimate (PDF)

Your materials at a glance

How to calculate concrete

  1. Measure the diameter. Of the form or hole, in inches.
  2. Measure the height or depth. In feet.
  3. Use the cylinder formula. π × (diameter ÷ 2)² × height, with the diameter in feet.
  4. For post holes, subtract the post. A 4×4 post is really 3.5 × 3.5 in: that space needs no concrete.

Worked example: six 10 in tube forms, 4 ft tall

  1. One tube: π × (10 ÷ 12 ÷ 2)² × 4 = 2.18 cu ft. Six tubes: 13.09 cu ft.
  2. Plus 5%: 13.74 cu ft = 0.51 cubic yards.
  3. 80 lb bags: 23.

Concrete per foot of round column or tube form

Diameter Cubic feet Cubic yards 80 lb bags
6 in 0.20 0.007 0.3
8 in 0.35 0.013 0.6
10 in 0.55 0.020 0.9
12 in 0.79 0.029 1.3
14 in 1.07 0.040 1.8
16 in 1.40 0.052 2.3
18 in 1.77 0.065 2.9
24 in 3.14 0.116 5.2

Per foot of height. Bags shown as a fraction: round up for the whole column.

Concrete per post hole (4×4 post)

Hole Cubic feet 80 lb bags 60 lb bags
8 in × 2 ft 0.53 1 2
10 in × 2 ft 0.92 2 3
10 in × 3 ft 1.38 3 4
12 in × 3 ft 2.10 4 5
12 in × 4 ft 2.80 5 7

One hole, 4×4 post (3.5 × 3.5 in actual), no waste included.

Concrete formulas by shape

All measurements in feet; divide inches by 12 first. Results are in cubic feet.

Column / pier
π × (diameter ÷ 2)² × height
Post hole
(hole area − post area) × depth; round hole π × (diameter ÷ 2)², square hole width²
Tube / ring
π × [(outer ÷ 2)² − (inner ÷ 2)²] × height

Cubic yards = cubic feet ÷ 27.

Frequently asked questions

How many bags of concrete per fence post?

It depends on the hole: a 10 in hole 2 ft deep around a 4×4 post takes about 0.92 cubic feet, so 2 bags of 80 lb. See the table below.

How big should a post hole be?

A common rule of thumb is a hole about three times as wide as the post and about a third to a half as deep as the post's height above ground. Check local frost depth.

How much concrete is in a tube form?

A 12 in tube holds about 0.79 cubic feet per foot of height, an 8 in tube about 0.35.

About the prices

Costs are estimated ranges with source and date, never a quote. Enter your local prices under "Use your own prices", or read how we estimate prices.