How to use it
- Enter the base length in feet.
- Enter the base width in feet.
- Enter the thickness in inches.
- Get cubic yards, bags, and cubic feet instantly.
This concrete base calculator tells you exactly how much concrete to order for a slab, pad, or footing. It takes your length, width, and thickness, then shows the total in cubic feet, cubic yards, and 80-lb bags. That matters because ordering too little means a cold joint and a weak base; ordering too much wastes money. For example, a 10 ft by 10 ft slab at 4 inches thick is about 33.3 cubic feet, which equals 1.23 cubic yards and about 56 bags. Read the cubic yards when ordering from a ready-mix supplier, and read bags when mixing on site. Always round up to the next whole bag or quarter yard. Use the numbers to budget accurately and avoid multiple trips to the store.
Pro tips
- Add 10% waste for spillage, uneven subgrade, or slight overdig.
- Round bag count up to the nearest full bag—never down.
- For ready-mix, round to the nearest quarter cubic yard and confirm with the supplier.
- Don't mix units: keep length and width in feet, thickness in inches.
Real-life examples
- Pouring a 10x10 patio slab and needing to know how many bags to buy.
- Calculating concrete for a shed base pad before ordering ready-mix.
- Estimating a walkway base so you don't run short mid-pour.
Case study
Before, Mark guessed his 10x10x4-inch shed base needed 45 bags and ran out halfway. After using this calculator, he saw he needed about 56 bags, ordered 60 with waste, and finished the pour in one trip.