How to use it
- Enter length in feet.
- Enter width in feet.
- Enter thickness in inches.
- Read the square footage and cubic yards displayed.
What it does – The calculator takes the length and width you enter (in feet) to give the total square footage of the slab. It then converts the thickness you type (in inches) to feet, multiplies the three dimensions to get cubic feet, and finally divides by 27 to show how many cubic yards of concrete you’ll need.
Why it matters – Knowing square footage helps you estimate material costs and labor, while the concrete volume tells you exactly how much mix to order, avoiding costly over‑orders or shortfalls.
How to read the results – Square Footage is the surface area (sq ft). Concrete Needed is the volume in cubic yards (yd³), rounded to two decimals.
Example – 12 ft × 10 ft × 4 in gives 120 sq ft and 1.48 yd³ of concrete.
Pro tips
- Add 5‑10% waste to the cubic yard total to cover spillage and uneven subgrade.
- Round square footage up to the nearest whole number for easier material ordering.
- Order concrete in 0.5 yd increments if your supplier allows, to reduce excess.
- Double‑check that thickness is entered in inches, not feet, before calculating.
Real-life examples
- A homeowner planning a 12 ft × 15 ft driveway wants to know how much concrete to order.
- A contractor estimating material for a 20 ft × 30 ft warehouse floor slab.
- A landscape designer sizing a patio and needing accurate volume for budgeting.
Case study
Before using the calculator, Mark guessed he needed 2 yd³ for his 15 ft × 20 ft patio and over‑ordered, wasting $200. After entering 15 ft, 20 ft, 5 in he saw the exact need was 1.85 yd³, ordered precisely, and saved material and cost.