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Footing & Foundation Concrete Calculator

Estimate cubic feet, cubic yards, and pre-mixed bag counts for deck footings, pad footings, and foundation pours. Adjust waste margin for spillage and overfill.

Project Dimensions

ft
in
in
10%
0%30%

Live Results

Volume per Footing

20.00cu ft

Total Volume

20.00cu ft

Total Volume (cu yd)

0.81cu yd

60 lb Bags

49

80 lb Bags

37

Includes 10% waste allowance · Bags rounded up

How to Use This Footing Calculator

  1. Measure footing length. Enter the footing length in feet along the direction of the pour. For continuous strip footings, use the total run length. For isolated pad footings, enter the length of one footing.
  2. Enter width and depth. Set footing width and depth in inches per your plan or local code. Common deck footings use 24 in × 24 in × 12 in; house foundations may require wider and deeper dimensions.
  3. Set number of footings. Enter how many identical footings you need. Multiply deck post count, column locations, or pad count. Each footing uses the same length, width, and depth values.
  4. Adjust waste margin. Use 10% waste for standard pours. Increase to 15–20% when using a pump, pouring in hot weather, or working with irregular excavation that causes spillage and overfill.
  5. Read order quantities. Review cubic yards for ready-mix delivery and bag counts for small DIY pours. Round up partial bags and confirm minimum load fees before ordering a short-load truck.

Formulas & Example

Footing volume is calculated as a rectangular prism. Width and depth entered in inches are converted to feet before multiplying by length. Total volume scales by the number of identical footings, then a waste factor is applied for ordering quantities.

Width (ft)  = Footing Width (in) ÷ 12
Depth (ft)  = Footing Depth (in) ÷ 12

Volume per Footing (cu ft) = Length (ft) × Width (ft) × Depth (ft)
Total Volume (cu ft)       = Volume per Footing × Number of Footings
Adjusted Volume            = Total Volume × (1 + Waste % ÷ 100)
Cubic Yards                = Adjusted Volume ÷ 27

60 lb Bags = Adjusted Volume ÷ 0.45  (rounded up)
80 lb Bags = Adjusted Volume ÷ 0.60  (rounded up)

Worked Example

A 10 ft × 24 in × 12 in footing (1 footing) at 10% waste: Width = 24 ÷ 12 = 2 ft. Depth = 12 ÷ 12 = 1 ft. Volume per footing = 10 × 2 × 1 = 20 cu ft. Total = 20 cu ft. With 10% waste: 20 × 1.10 = 22 cu ft. Cubic yards = 22 ÷ 27 = 0.81 CY. Bag counts: 22 ÷ 0.45 = 49 sixty-pound bags; 22 ÷ 0.60 = 37 eighty-pound bags (both rounded up).

Pre-mixed bag counts assume standard yields of 0.45 cu ft per 60 lb bag and 0.60 cu ft per 80 lb bag (Quikrete/Sakrete). Results are always rounded up to the nearest whole bag.

Frequently Asked Questions

What size concrete footing do I need for a deck?â–¾
Most residential deck footings use a 24 in × 24 in pad at 12 in deep, or a 12 in diameter sonotube filled to 12 in below grade. Heavier decks, hot tubs, or multi-level structures may require 30 in × 30 in pads at 16 in deep or larger. Always verify footing size against your local building code and frost depth requirements before pouring.
How much concrete is in a 24×24×12 inch footing?▾
A single 24 in × 24 in × 12 in pad equals 4 cu ft of concrete (2 ft × 2 ft × 1 ft). With a 10% waste allowance, plan for 4.4 cu ft — about 10 sixty-pound bags or 8 eighty-pound bags. For six identical deck footings, that totals roughly 26 cu ft or 0.96 cubic yards with waste included.
Should I use ready-mix or bagged concrete for footings?â–¾
Bagged concrete works well for a handful of deck or fence post footings where total volume stays under roughly 1 cubic yard. Ready-mix becomes more economical above that threshold, especially when pouring multiple house foundation footings or a continuous strip footing. Compare local short-load truck fees against bag costs and labor before deciding.
How deep should footings be below the frost line?â–¾
Footings must extend below the local frost line to prevent heave — typically 36 to 48 inches in northern climates and as little as 12 inches in southern regions. Depth is measured from finished grade to the bottom of the footing, not the top. Check your jurisdiction's adopted IRC or local amendment for the exact frost depth in your area.
How much waste should I add for footing pours?â–¾
Standard footing pours use a 10% waste factor to cover spillage, over-excavation, and uneven hole bottoms. Increase to 15% when pumping concrete into deep forms or pouring multiple footings from a single truck where leftover material is hard to reuse. This calculator applies your selected waste percentage to total volume and bag counts automatically.

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