How to use it
- Enter the foundation length in feet.
- Enter the width in feet.
- Enter the thickness in inches.
- Enter the price per cubic yard and click calculate.
This calculator turns your foundation's length, width, and thickness into the exact concrete volume you need, plus what it will cost. It also tells you how many standard 80-lb bags to buy and the total cubic feet. Why does that matter? Because ordering too little concrete means a cold joint and a weak foundation; ordering too much means wasted money. The results are broken down into: Cubic yards – the unit ready-mix suppliers quote; Estimated cost – multiply your price per yard by the volume; Bags – each 80-lb bag yields 0.6 cubic feet, so the calculator divides the total cubic feet by 0.6; Cubic feet – a handy unit for small jobs. Use the numbers to compare ready-mix vs. bagged concrete, plan your budget, and avoid last-minute trips to the store. It's instant, accurate, and free.
Pro tips
- Add 5–10% waste for spillage, uneven subgrade, or slight over-excavation—never order exact volume.
- Round up your cubic yards when ordering ready-mix; suppliers won't deliver a partial yard.
- If using bags, round up to the nearest full bag and buy a few extra from the same batch.
- Don't confuse cubic feet with cubic yards—there are 27 cubic feet in a yard, so check the calculator's units.
Real-life examples
- A homeowner pricing a 20×30 ft shed foundation at 4 inches thick.
- A contractor estimating the concrete needed for a house footing with 2-foot width and 1-foot depth.
- A DIYer comparing bagged mix vs. ready-mix for a small 8×10 ft patio slab.
Case study
Mark planned a 12×16 ft garage foundation, 6 inches thick. He guessed 4 cubic yards and nearly over-ordered. Using this calculator, he entered his numbers, got 3.56 cubic yards, added 5% waste, and ordered 3.75 yards—saving $120 and avoiding a truckload of leftover concrete.