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Deck Estimate Tools

Deck Footing Concrete Calculator

Estimate concrete volume and bag count for your deck footings. Choose circular or square footings, set depth and count, and edit the bag yield to match your product.

Units
Footing shape

Below grade, per your footing design

80lb ~0.6, 60lb ~0.45, 50lb ~0.375 cu ft

Estimate

Bags to buy(incl. 10% waste)26
Volume per footing2.356 cu ft
Total volume14.137 cu ft
Total volume0.524 cu yd
Total volume0.40032 m³
Bags before waste24

Anyone with this link can view the deck measurements included in it.

Intermediate calculation

Volume per footing = π × (diameter ÷ 2)² × depth. Total = per footing × count. Bags = ceil(total × (1 + waste) ÷ bag yield).

Follow your product packaging

Use the yield printed on the concrete product packaging. Bag weight alone does not guarantee an exact volume across all products. Confirm footing size and depth against local code and frost-depth requirements.

How to use this calculator

  1. Enter the number of footings and pick circular or square.
  2. Enter the diameter, or the width and length for square footings.
  3. Enter the depth of concrete per footing.
  4. Set the bag yield to match your product and choose a waste factor.

Formula with a worked example

circular: volumePerFooting = pi × (diameter/2)² × depth
square: volumePerFooting = width × length × depth
totalCubicFeet = volumePerFooting × footingCount
bags = ceil(totalCubicFeet × (1 + waste) / bagYield)

For six 12 in round footings, 36 in deep, 0.6 cu ft bags, 10% waste:

perFooting = pi × (0.5)² × 3 = 2.356 cu ft
total = 2.356 × 6 = 14.14 cu ft (0.524 cu yd)
bags = ceil(14.14 × 1.10 / 0.6) = 26

Common bag yields

  • 80 lb bag: about 0.60 cubic feet.
  • 60 lb bag: about 0.45 cubic feet.
  • 50 lb bag: about 0.375 cubic feet.

These are editable estimates. The exact yield is printed on your product packaging.

Waste-factor guidance

Concrete is lost to spillage, over-excavated holes, and mixing. A 10% allowance is common; use 15% for irregular or hand-dug holes. See the waste factor guide.

Common mistakes

  • Entering diameter where radius is expected. Enter the full diameter.
  • Mixing inches and feet. Keep every dimension in the selected unit.
  • Using a generic bag yield instead of the printed value.
  • Forgetting that over-dug holes need more concrete.

Limitations & safety notice

Footing design is set by code

This tool estimates concrete volume and bag count for the dimensions you enter. It does not determine required footing size, depth, frost protection, or bearing capacity. Confirm footing design with your local building department and follow the concrete product instructions.

Related deck calculators

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Frequently asked questions

Methodology & review

This calculator uses the transparent formulas shown above. It estimates material quantities only and does not evaluate structural safety or local code compliance. See our methodology for assumptions and rounding rules. Last reviewed: August 14, 2026.