Concrete Countertop Calculator
Estimate concrete and weight for a DIY concrete countertop, including sink or cooktop cutouts.
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Short answer
A standard 8-foot countertop slab (96×26 in) at 1.5 inches thick needs roughly 3.1 cubic feet of concrete, or about 9 bags of 50 lb specialty countertop mix. Cutting out space for a sink reduces the volume slightly and should be subtracted before ordering material.
Reference: thickness by use case
| Application | Typical thickness | Notes |
|---|---|---|
| Standard kitchen counter | 1.5–2 in | Reinforce with mesh or rebar |
| Thin / GFRC-style top | 0.75–1.25 in | Requires glass-fiber reinforced mix |
| Outdoor bar or island top | 2 in | More resistant to chipping at edges |
How to plan a concrete countertop pour
- Measure the finished countertop footprint, including any overhangs.
- Mark and measure any sink or cooktop cutout, then check the box above to subtract it from the total.
- Use a countertop-specific concrete mix (finer aggregate, lower water ratio) for a smoother, less porous finish.
- Build a melamine or plastic-lined form, and reinforce with wire mesh or rebar set at mid-depth.
- Vibrate the form after pouring to release trapped air bubbles, which cause pitting on the finished surface.
- Cure under plastic for at least 5–7 days, then grind, polish, and seal before installation.
Worked example
- Slab
- 96 × 26 × 1.5 in = 3,744 in³ = 2.17 ft³
- Sink cutout
- 33 × 22 × 1.5 in = 1,089 in³ = 0.63 ft³
- Net with 10% waste
- (2.17 – 0.63) × 1.10 = 1.69 ft³
- Bags (50 lb, 0.375 ft³ each)
- ceil(1.69 / 0.375) = 5 bags
Common mistakes
- Pouring too thin without reinforcement, leading to cracking once the countertop is moved or installed.
- Not vibrating the mix, which leaves visible air pockets (‘bug holes’) on the finished face.
- Forgetting to subtract sink or cooktop cutouts, which overestimates material and weight.
- Skipping a sealer, which leaves the porous surface vulnerable to staining from oil, wine, and acidic foods.
Assumptions
- Density assumed at 150 lb per cubic foot for standard mix; specialty countertop mixes can vary slightly.
- Bag yields follow manufacturer averages: 80 lb = 0.60 ft³, 60 lb = 0.45 ft³, 50 lb = 0.375 ft³, 40 lb = 0.30 ft³.
- Cutout is treated as a simple rectangle; irregular cutouts should be approximated conservatively.
- Does not include reinforcement, forms, pigments, sealer, or polishing supplies.
Frequently asked questions
How thick should a concrete countertop be?
1.5 to 2 inches is standard for a kitchen countertop with reinforcement. Thinner pours (under 1.25 inches) are possible but usually require a glass-fiber reinforced concrete (GFRC) mix to stay strong.
How much does a concrete countertop weigh?
At roughly 150 lb per cubic foot, a typical 1.5-inch-thick kitchen countertop weighs about 19 lb per square foot — heavy enough that cabinets and support need to be checked before installation.
Do I need to subtract the sink cutout?
Yes. Subtracting the cutout area gives a more accurate concrete volume and avoids over-ordering material, though it’s good practice to round up slightly for waste.