Whether you're looking to add onto an existing concrete slab or planning on breaking one up for disposal and replacement, knowing the volume of a piece of concrete can help in many an improvement project. While determining the exact volume is impossible without a detailed measurement of the slab on all sides, including the bottom concealed by soil, a close estimate is possible with a few short mathematical calculations.
Things You'll Need
 Tape measure
 Shovel
 Pole
 Carpenter's level
 Grease pencil
 Calculator

Determine the surface area of the concrete by measuring the length and the width of the slab in inches with a tape measure. Multiply the length by the width and write the resulting surface area down.

Dig a small hole alongside the slab until you reach the slab base. Stick a pole down the hole until you reach the base. Check that the pole is plumb, sticking straight up at a 90 degree angle from the ground, using a carpenter's level. Mark the location of the top of the slab on the pole with a grease pencil.

Pull the pole from the hole and measure the distance from the pole tip that sat against the bottom of the slab and the grease mark. Mark the height of the slab down in inches.

Multiply the surface area of the slab by its height to get the volume of the slab in cubic inches.

Convert the volume in cubic inches into cubic yards by dividing the cubic inches by 46,656 (36by3636).
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