Concrete Footing Calculator
Concrete volume and bag quantities for round, square or rectangular footings.
Project inputs
Examples
Supplier prices (optional)
Prices exclude delivery, tax and labor. Currency changes labels only.
Estimate
Start with your measurements.
Your order quantity, purchasing options and material cost appear here.
Overage is included in purchasing quantities. Check product yields before ordering.
Check product yields and project specifications. Material subtotals exclude delivery, tax, labor and equipment. These quantities do not specify structural dimensions or reinforcement.
Estimate
Confirm supplier order increments.
Ordering notes
Worked example
Here is a step-by-step walkthrough for 4 round deck footings, each 12 inches in diameter and 36 inches deep; a worked geometry example, not a footing specification.
- Step 1; Radius 12 in ÷ 2 = 6 in = 0.5 ft
- Step 2; Single Volume π × 0.5² × 3 ft = 2.36 cu ft
- Step 3; All Footings 2.36 × 4 = 9.42 cu ft
- Step 4; Add 10% Waste 9.42 × 1.10 = 10.36 cu ft
- Step 5; Cubic Yards 10.36 ÷ 27 = 0.38 cu yd
- Step 6; 60 lb Bags 10.36 ÷ 0.45 = 24 bags
Calculation method
The calculator computes the volume of each footing based on its shape: round footings use π × r² × depth; square footings use side² × depth; rectangular footings use length × width × depth. It then multiplies by your footing count and adds a waste factor.
Volume is then converted to cubic yards and split into bag counts for both 60 lb and 80 lb mixes. Cost estimates multiply bag count or cubic yards by your supplied prices.
Pro tip: For footings under 1 cubic yard total, bagged concrete with tube forms (Sonotubes) is the standard approach. For large projects with many footings, a ready-mix order may save significant time and cost.
Project notes
- Confirm footing depth. Use the specified depth for the project and local conditions, including frost requirements.
- Use Sonotube (tube form) for round footings. Cardboard tube forms keep the shape, reduce blowouts, and make it easy to pour by yourself. Available at any hardware store, they're cheap and well worth it.
- Check the hardware detail. Coordinate anchors and post bases with the specified installation method before pouring.
- Follow curing and loading instructions. Use the concrete product and project specification; volume alone does not determine safe loading time.
- Don't add extra water to the mix. It might seem easier to pour but it weakens the concrete significantly. Follow bag instructions exactly.
- Whole bags: Bag quantities round up. Confirm bag yield and the supplier’s return policy.
Input and ordering checks
Footings too shallow. The most common and costly error. A footing above the frost line will shift seasonally, causing structural problems that are expensive to fix.
Wrong diameter. Undersized footings can't spread the load and may punch through soft soil. Use the rule of thumb: footing diameter = 3× the post width, then verify with your local code.
Skipping the gravel base. Pouring directly onto soft or wet soil leads to settlement. Place 4–6 inches of compacted gravel first to provide drainage and a stable base.
Unit confusion. This calculator accepts diameter and depth in inches (converted internally). Make sure you're not mixing feet and inches in your inputs.
Assumptions
QUIKRETE Concrete Mix technical data provides the 0.45 ft³ and 0.60 ft³ bag yields used here. Other mixes can have different yields.
- ◦Concrete yield: 60 lb bags = 0.45 cu ft; 80 lb bags = 0.60 cu ft. Standard manufacturer figures.
- ◦Waste factor: Default 10% covers spillage and tube overfill. Increase to 15% for difficult pours or irregular excavations.
- ◦Round footing formula: π × r² × depth, where r = diameter ÷ 2. All dimensions converted to feet before calculation.
- ◦Prices vary: Bag and ready-mix prices vary by region and season. Update the input fields to match your local supplier pricing.
- ◦Results are estimates: Confirm quantities with your supplier before ordering. Field conditions may vary.