How to calculate granite weight
Granite is a dense, solid stone, so its weight is simply volume × density:
volume (cu ft) = length (ft) × width (ft) × thickness (ft)
weight (lb) = volume × about 168 lb per cu ft
The calculator lets you enter length and width in one unit and thickness in another, because countertops are usually measured in inches with a thickness in centimeters. It converts everything to feet first: inches ÷ 12, centimeters ÷ 30.48.
Worked example: a countertop run
A countertop 108 inches long and 26 inches deep, 3 cm thick:
- Area: 108 × 26 = 2,808 sq in = 19.5 sq ft
- Thickness: 3 ÷ 30.48 = 0.0984 ft
- Volume: 19.5 × 0.0984 = 1.92 cu ft
- Weight: 1.92 × 168 = about 322 lb (311–336 lb across the usual range of granite densities)
Sink and cooktop cut-outs reduce that a little. Edge build-ups (a laminated thicker edge) add some back.
Granite density
Granite is mostly quartz and feldspar with some mica and dark minerals. Its density sits in a fairly tight band:
| Unit | Typical granite | Range |
|---|---|---|
| Pounds per cubic foot | 168 | 162–175 |
| Pounds per cubic inch | 0.097 | 0.094–0.101 |
| Kilograms per cubic meter | 2,690 | 2,600–2,800 |
| Specific gravity | 2.69 | 2.6–2.8 |
| Tons per cubic yard (solid) | 2.27 | 2.19–2.36 |
Darker “granites” sold for countertops are sometimes other rocks, such as gabbro or basalt, which can be denser. If your stone is very dark, try the basalt setting (about 180 lb per cu ft) as an upper estimate.
Granite weight per square foot
For flat slabs, it is handy to know the weight per square foot of face:
| Thickness | Inches | About lb per sq ft (168 lb/cu ft) | Range |
|---|---|---|---|
| 2 cm | ¾” | 11.0 | 10.6–11.5 |
| 3 cm | 1¼” | 16.5 | 15.9–17.2 |
| 1¼” | 1.25” | 17.5 | 16.9–18.2 |
| 2” | 2” | 28.0 | 27.0–29.2 |
| 4” | 4” | 56.0 | 54.0–58.3 |
Multiply by the area for a quick estimate. A kitchen island top of 96 × 42 inches (28 sq ft) is about 460 lb in 3 cm or 310 lb in 2 cm. A large 3 cm slab of 120 × 65 inches (54 sq ft) is about 900 lb.
Granite blocks, steps and posts
| Piece | Size | Volume | About weight |
|---|---|---|---|
| One cubic foot | 12 × 12 × 12 in | 1 cu ft | 168 lb |
| Landscape step | 48 × 14 × 6 in | 2.33 cu ft | 390 lb |
| Bench slab | 72 × 18 × 4 in | 3.0 cu ft | 500 lb |
| Square post | 10 × 10 × 48 in | 2.78 cu ft | 470 lb |
| Block | 2 × 2 × 2 ft | 8 cu ft | 1,340 lb |
For rounded granite boulders, switch the calculator’s shape to Boulder, or use the boulder weight calculator, which explains the ellipsoid formula.
Solid granite versus crushed and decomposed granite
Weight per cubic yard depends on whether the granite is one piece or a pile:
- Solid granite: about 4,500 lb per cubic yard.
- Crushed granite chips: about 2,500–2,900 lb per loose cubic yard; see the stone calculator.
- Decomposed granite: about 2,400–2,900 lb per loose cubic yard, more once compacted; see the decomposed granite calculator.
Handling heavy granite safely
A 3 cm countertop run of 300+ lb is a job for several people and the right carrying gear, and slabs are carried on edge, not flat, because they can crack under their own weight when laid flat without support. For anything larger, use equipment rated well above the estimated weight. Cabinets under a granite top must be level and sound; check the fabricator’s support requirements for overhangs.
The calculator gives the weight of solid stone from its dimensions. Real slabs vary with the stone's mineral content, resin treatments and cut-outs. For lifting or structural decisions, use the fabricator's or supplier's figure and leave a margin.
Questions people ask
- How much does granite weigh per cubic foot?
- About 162 to 175 pounds per cubic foot, depending on the granite. The calculator uses 168 pounds, which corresponds to a specific gravity of about 2.69 (2,690 kg per cubic meter).
- How much does a granite countertop weigh per square foot?
- By the solid-stone math, about 11 pounds per square foot for a 2 cm (¾ inch) slab and about 16.5 pounds per square foot for a 3 cm (1¼ inch) slab. Denser stones and resin-treated slabs can be a little heavier; your fabricator can give the figure for your slab.
- How do you calculate the weight of granite?
- Convert length, width and thickness to feet, multiply them to get cubic feet, then multiply by about 168 pounds per cubic foot. A 108 × 26 inch countertop that is 3 cm thick is 1.92 cubic feet, or about 322 pounds.
- How much does a cubic yard of granite weigh?
- Solid granite weighs about 4,500 pounds (2.27 tons) per cubic yard. Crushed granite in a loose pile weighs much less, about 2,500 to 2,900 pounds per cubic yard, because of the air between the pieces.
- How heavy is a granite slab?
- Multiply its area in square feet by about 16.5 for 3 cm or about 11 for 2 cm. A large 3 cm slab of 120 × 65 inches (54 square feet) weighs roughly 900 pounds.