Concrete Column Calculator
Professional concrete column calculator for circular or rectangular columns. Compute volume, waste, weight, cost, and ready-mix bags with WCAG-compliant, mobile-first UX.
Project Inputs
Start by selecting the column shape, units, and key dimensions below.
Unit system
Column shape
Bags required (rounded up)
40 lb bag (0.30 ft³)
60 lb bag (0.45 ft³)
80 lb bag (0.60 ft³)
20 kg bag (~0.009 m³)
25 kg bag (~0.012 m³)
30 kg bag (~0.014 m³)
How to use this calculator
This tool converts the supplied dimensions into a single volume per column, scales it to the number of columns, adds the selected waste allowance, and presents all outputs in imperial and metric units. Enter the shape, choose the length units, and fill in the required dimensions—diameter for cylindrical columns or width and depth for rectangular members.
Methodology
The calculator computes a fixed-rate volume for each column (πr²h for circular, W·T·H for rectangular) and multiplies that volume by the column count. Waste allowance inflates the total by the requested percentage. Density is applied in the selected unit system but converted to kilograms per cubic meter internally, ensuring consistent mass output. Cost estimates use the chosen unit price and display the total in the corresponding currency unit.
Typical inputs reflect ACI 211.1 guidance and QUIKRETE manufacturer yields; see the citations below for the exact references.
Full original guide (expanded)
Data source & assumptions
American Concrete Institute (ACI 211.1) defines the normal-weight concrete density range (~145–155 lb/ft³ or 2320–2480 kg/m³). QUIKRETE bag yields anchor the ready-mix conversions (40 lb → 0.30 ft³, 60 lb → 0.45 ft³, 80 lb → 0.60 ft³, metric bags at ~0.009–0.014 m³).
Glossary of variables
- D: Column diameter
- W: Column width (rectangular)
- T: Column depth/thickness (rectangular)
- H: Column height
- V: Volume of a single column
- n: Number of identical columns
- w: Waste allowance (%)
- V_total: Total concrete volume including waste
- ρ (rho): Concrete density (kg/m³ or lb/ft³)
- m: Mass (kg or lb)
Step-by-step example
Scenario: 4 circular columns with a diameter of 12 in, height of 10 ft, and 7% waste.
- Convert to consistent units: D = 12 in = 1 ft, H = 10 ft.
- Single column volume = π × (0.5 ft)² × 10 ft ≈ 0.291 yd³ (7.85398 ft³).
- Total before waste = 4 × 0.291 yd³ = 1.165 yd³.
- Add waste: 1.165 yd³ × 1.07 = 1.246 yd³.
- 80 lb bags (0.60 ft³): 1.246 yd³ → 56.1 ≈ 57 bags.
Using ρ = 2400 kg/m³, the total volume translates to ≈0.952 m³ and a mass of roughly 2285 kg.
Frequently Asked Questions
Does this calculator include footing or pedestal volumes?
No. Only the column is modeled. Add footing volumes separately when needed.
Should I deduct the volume of rebar?
The steel volume is usually negligible for small-to-medium columns. For heavily reinforced members, subtract the steel manually.
What density should I choose?
Lightweight mixes: 1600–2000 kg/m³; heavyweight mixes: above 2600 kg/m³. Use mix-specific data when accuracy matters.
How much waste should I allow?
Common practice is 5–10%. Increase for complex forms, windy conditions, or long pump runs.
Are bag yields consistent across brands?
They vary slightly. Verify the product sheet and always round up counts.
Can I mix units for diameter and height?
Yes. Switch the global length unit before typing each dimension; the calculator converts internally.
How does this compare to ready-mix orders?
The tool outputs both cubic yards (US) and cubic meters (SI) so you can order the correct quantity from a supplier.