How to Calculate Concrete Volume for a Slab or Footing

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To figure out concrete volume for a slab or footing, measure the length, width, and thickness in feet, then multiply those numbers together to get cubic feet. Divide that result by 27 to convert to cubic yards, which is how concrete is typically ordered. Remember to add a little extra for spillage or uneven subgrades—about 10 percent more is a good rule of thumb.