The Concrete Footing Volume Calculator works out exactly how much concrete to order for any footing — whether it is a rectangular spread footing for a wall or shed, or a round tube footing (Sonotube) for a deck post, fence post, or pergola column. Enter your footing dimensions in imperial (feet and inches) or metric (m..
US average: $125–$165/CY ready-mix (2025)
RESULTS
VOLUME EACH (net)
0.148 CY
= 4.00 cubic feet
WITH 10% WASTE — order this amount
0.163 CY
80 LB BAGS
7
60 LB BAGS
9
ESTIMATED MATERIAL COST
$21
FOOTING VISUALISER (not to scale)
FOOTING SUMMARY
TYPICAL FOOTING DEPTHS
Light shed, pergola
Above frost — mild climates
Fence post footing
⅓ post height minimum
Deck post (standard)
Below frost, most US states
Deck post (northern)
MN, WI, northern states
Deep frost/structural
Check local building code
UNIT CONVERSIONS
1 cubic yard = 27 cubic feet
1 cubic yard ≈ 0.765 m³
80 lb bag ≈ 0.6 cubic feet
60 lb bag ≈ 0.45 cubic feet
25 kg bag ≈ 0.01 m³
Always order 10% extra for waste
Choose your unit system — Imperial (feet and inches, standard for US) or Metric (metres and millimetres) — then select your footing shape: Rectangular for spread footings and pad footings, or Round for tube footings (Sonotube/form tube) used under deck posts and fence posts.
Enter your footing dimensions. For rectangular footings, enter Length, Width, and Depth. For round footings, enter the tube Diameter and Depth. Use the preset buttons for the most common sizes — 2 ft × 2 ft × 12 inches for a light shed footing, 12-inch diameter × 48 inches for a standard deck post.
Enter the number of identical footings in your project. If you have footings of different sizes, calculate each size separately and add the totals. The calculator multiplies the single-footing volume by your count to give a combined order quantity.
Optionally enter your local concrete price per cubic yard (US) or cubic metre (metric) to get a material cost estimate. US ready-mix averages $125–$165 per CY in 2025; check with your local batch plant for exact pricing.
Read the results: Volume per footing (net), volume per footing with 10% waste added, total volume for all footings with waste, equivalent bag count for hand-mixing, and estimated material cost. Always order the +10% figure — running short mid-pour creates a structurally weak cold joint.
Calculating concrete for 8 deck post footings, 12-inch Sonotube, 48 inches deep: Step 1: Convert to feet Diameter: 12 in ÷ 12 = 1.00 ft → radius = 0.50 ft Depth: 48 in ÷ 12 = 4.00 ft Step 2: Volume per footing (cylinder formula: π × r² × depth) = 3.14159 × 0.50² × 4.00 = 3.14159 × 0.25 × 4.00 = 3.142 cubic feet = 3.142 ÷ 27 = 0.116 cubic yards Step 3: Add 10% waste per footing = 0.116 × 1.10 = 0.128 CY per footing Step 4: Total for 8 footings = 0.128 × 8 = 1.026 CY → order 1.1 CY (round up to nearest 0.25 CY) Step 5: Bag count if hand-mixing (not recommended at this volume) = 3.142 cu ft × 8 footings = 25.1 cu ft total = 25.1 ÷ 0.6 = 42 bags (80 lb) → at this quantity, order ready-mix instead Step 6: Material cost at $140/CY = 1.026 CY × 1.10 × $140 = $158 for concrete material
Last updated: April 29, 2026 · Formula verified by EagleCalculator team · Eagle-eyed accuracy for every calculation.