How do I calculate concrete for a round column?

Volume = π × (diameter ÷ 2)² × height. Enter diameter and height — the calculator converts to cubic feet, yards, and bags.

How many 80 lb concrete bags do I need?

Divide your volume in cubic feet by the bag yield (80 lb ≈ 0.60 ft³ per bag), add your waste factor, then round up. Our calculator does this live — e.g. a 12×10×4 in slab with 10% waste needs 74 bags.

Should I buy bags or ready-mix?

Small jobs under ~1 yd³ are usually cheaper and easier with bags. Larger slabs and driveways are ordered by the cubic yard from a ready-mix supplier. We show both bag count and order-ready yards.

Concrete Column Calculator

For deck posts, fence piers, and round columns, enter diameter and height. Volume uses π × r² × h — results show bags and order-ready yards.

No signup
Formula shown
Free forever

Dimensions

Shape

Units

Diameter (in)

Height (ft)

Number of identical pours

Spillage & Waste (10%)Includes extra so you don't run short

Bag size

Using a pump truck?

Adds 0.5 yd³ to fill the priming lines

Price per bag ($, optional)

Price per yd³ ($, optional)

Result

6 bags (80 lb)

0.1280 yd³ with 10% waste · order 0.25 yd³ ready-mix

How we calculated it

Column: π × (12 in ÷ 2)² × 4 ft = 3.14 ft³
+10% waste = 3.46 ft³
3.46 ft³ ÷ 27 = 0.1280 yd³

Yield based on Quikrete/Sakrete published data: 0.60 ft³ per 80 lb bag. Formula: L × W × (T/12) ÷ 27 = yd³. Full methodology

Plan the rest of your project

Embed this calculator on your site

Copy the iframe code below. Free to use — include the attribution link shown in the embed.

<iframe src="https://qtycalc.com/embed/concrete" width="100%" height="780" style="border:1px solid #e5e7eb;border-radius:8px;" title="Concrete Calculator" loading="lazy"></iframe>

For deck posts, fence piers, and round columns, enter diameter and height. Volume uses π × r² × h — results show bags and order-ready yards.

Frequently asked questions

How do I calculate concrete for a round column?: Volume = π × (diameter ÷ 2)² × height. Enter diameter and height — the calculator converts to cubic feet, yards, and bags.
How many 80 lb concrete bags do I need?: Divide your volume in cubic feet by the bag yield (80 lb ≈ 0.60 ft³ per bag), add your waste factor, then round up. Our calculator does this live — e.g. a 12×10×4 in slab with 10% waste needs 74 bags.
Should I buy bags or ready-mix?: Small jobs under ~1 yd³ are usually cheaper and easier with bags. Larger slabs and driveways are ordered by the cubic yard from a ready-mix supplier. We show both bag count and order-ready yards.

Frequently asked questions

Related calculators & guides