Concrete Footing Calculator – Guide & Formulas
Calculate the total concrete volume and pre-mix bags needed for cylinder tube piers or square footings.
Determine the exact cubic yards of concrete, number of premixed bags, and structural tubes needed for deck footings, structural column piers, or post holes. Supports circular, square, and bell-bottom shapes.
Key Takeaway
Use the free Concrete Footing Calculator to calculate the total concrete volume and pre-mix bags needed for cylinder tube piers or square footings. Get instant results with step-by-step explanations.
How to Use the Concrete Footing Calculator
- Choose circular Sono-tube style or rectangular/square pier shapes.
- Enter footing diameter or width, depth, and the total quantity of footings.
- Set your preferred waste factor (standard 5-10%) and get instant premix bags.
The Formula
Variable Definitions
- R: Radius of circular pier tube
- D: Depth of the footing excavation
- Q: Number of individual identical piers
Deck Pier Sono-Tubes
Calculate concrete for 8 cylindrical footing holes. Each pier is 12 inches in diameter and 48 inches (4 feet) deep.
- Step 1: Find the radius in feet: 6 inches = 0.5 feet.
- Step 2: Calculate volume of one cylinder: π × 0.5² × 4 = 3.1416 × 0.25 × 4 ≈ 3.14 cubic feet.
- Step 3: Multiply by quantity of footings: 3.14 × 8 = 25.13 cubic feet.
- Step 4: Convert to cubic yards: 25.13 / 27 ≈ 0.93 cubic yards. This requires approx. 57 bags of 80lb premix.
Frequently Asked Questions
What is a bell-bottom footing?
A bell-bottom footing flared outward at the base. This design distributes structural column loads over a wider surface area of soil, providing superior frost heave resistance.
How deep should structural deck piers be?
They must go below your region's frost line to prevent freeze-thaw cycles from lifting the deck. Check local building codes (often 36 to 48 inches deep).
What is a typical mix strength for structural columns?
Piers and columns usually require concrete with a compressive strength of at least 3,000 to 4,000 PSI.