Concrete Countertop Calculator

Measure in inches, cut out the holes

Countertops are small enough that inches are the right unit. Measure the cabinet run and add the overhang you want at the front and any open ends. Then work out the area of the sink and cooktop holes and enter it as square inches.

In the worked example, a 96 x 25.5 in top at 1.5 in thick, with 480 sq in of cutouts, holds 1.71 cu ft of concrete. With 10% added that is 4 bags of 80 lb mix.

The weight is the real design question

That same 8 ft top weighs about 256 lb when finished, or 18.8 lb per square foot. An island 72 x 36 in at 2 in thick reaches about 450 lb. Cabinets, brackets and the floor under them must be up to it.

If the top is cast in place, the cabinets carry it from day one. If it is cast in a shop or garage and set later, plan how many people it takes to lift and carry it.

Mix and thickness

Countertop mixes are made for a smooth, dense surface and are sold in bags like regular concrete. Check the yield printed on your mix; we assume about 0.6 cu ft per 80 lb bag.

Thicker tops look heavier and weigh much more. A thin top with a thicker built-up front edge gives the look of mass at a lower weight; run the edge as its own piece if you want an exact count.

Things the bag count leaves out

• Melamine or other smooth form board and silicone for the edges.
• Mesh or reinforcement suited to the mix you choose.
• Knockouts for the sink and faucet holes.
• Sealer for the finished surface.

Related tools

The concrete weight calculator gives weight for any thickness and density. If the countertop is part of a larger remodel, the kitchen remodel cost calculator helps with the overall budget.