Concrete Footing Calculator
Calculates the cubic yards of concrete needed for rectangular foundation footings. Use this before ordering ready-mix concrete for decks, fences, or structural foundations.
About this calculator
Foundation footings are rectangular prisms, so their volume is found by multiplying length × width × depth. Because concrete is ordered in cubic yards and measurements are typically taken in feet, you must divide the cubic-foot volume by 27 (since 1 cubic yard = 27 cubic feet). The formula is: Volume (yd³) = (footingLength × footingWidth × footingDepth) / 27. For multiple footings, calculate each individually and sum the results. Always add 5–10% extra to account for spillage, over-excavation, and uneven soil surfaces. Accurate footing volume estimates prevent costly last-minute concrete orders on job sites.
How to use
Suppose you are pouring a footing that is 10 feet long, 2 feet wide, and 1.5 feet deep. Step 1 — Multiply the dimensions: 10 × 2 × 1.5 = 30 cubic feet. Step 2 — Convert to cubic yards by dividing by 27: 30 / 27 ≈ 1.11 cubic yards. Step 3 — Add a 10% waste buffer: 1.11 × 1.10 ≈ 1.22 cubic yards. You would order at least 1.25 cubic yards of ready-mix concrete for this single footing.
Frequently asked questions
How many cubic yards of concrete do I need for a 12-foot footing?
It depends on the width and depth of the footing as well. Using the formula (length × width × depth) / 27, a 12 ft × 2 ft × 1 ft footing equals 24 / 27 ≈ 0.89 cubic yards. Always add a 5–10% waste factor before ordering. Ready-mix suppliers typically have a minimum order, so check with your local plant.
Why is concrete measured in cubic yards instead of cubic feet?
Concrete suppliers price and deliver material by the cubic yard because it results in more manageable numbers for large pours. One cubic yard equals 27 cubic feet, so dividing your cubic-foot volume by 27 gives the industry-standard unit. This convention is used across North America for ready-mix ordering and batching plant calculations.
What happens if I underestimate concrete for my footings?
Running short of concrete mid-pour is a serious problem because a cold joint — where fresh concrete meets a partially set pour — creates a structural weak point. You would need to order an emergency batch, which may cost significantly more and delay your project. It is always better to over-order by 5–10% than to risk a structural deficiency in your foundation.