Granite Weight Calculator
Find granite weight per square foot in kg and lbs for 18 mm, 20 mm and 30 mm slabs, or calculate a full slab, countertop or block from its dimensions.
Quick Answer
Granite weighs about 170 lbs per cubic foot (2,723 kg/m³). Per square foot that is roughly 4.55 kg (10.0 lbs) at 18 mm, 5.06 kg (11.2 lbs) at 20 mm, and 7.59 kg (16.7 lbs) at 30 mm. Multiply length × width × thickness in feet, then by 170, to get the weight in pounds.
Granite Weight Calculator (Weight per Sq Ft in kg & lbs) Guide
The granite weight calculator works out how much a piece of granite weighs from its dimensions. Enter the length, width and thickness of a slab, countertop or block and it returns the weight in pounds and tons using granite's density of about 170 pounds per cubic foot. That number matters long before installation day: it decides whether two people can carry a piece, whether a cabinet run needs extra support, and whether your vehicle is rated to move it.
Granite is one of the denser stones used in building. At 170 lbs per cubic foot it is heavier than limestone or sandstone (both around 150) and close to marble and travertine. A full 3 cm slab of around 50 square feet weighs roughly 900 pounds, which is why fabricators move them upright on A-frames rather than flat.
Granite Weight per Square Foot in kg and lbs
Weight per square foot scales directly with thickness, so once you know the thickness you can read the figure straight off. Granite is sold as 18 mm and 20 mm in much of Asia and as 2 cm and 3 cm in North America and Europe — the table covers both conventions.
Granite weight per square foot and per square metre, by slab thickness
| Thickness | kg per sq ft | lbs per sq ft | kg per m² |
|---|---|---|---|
| 18 mm | 4.55 kg | 10.0 lbs | 49.0 kg |
| 20 mm (2 cm) | 5.06 kg | 11.2 lbs | 54.5 kg |
| 30 mm (3 cm) | 7.59 kg | 16.7 lbs | 81.7 kg |
| 50 mm (2 inch) | 12.65 kg | 27.9 lbs | 136.2 kg |
One point worth watching: 2 cm is often called "3/4 inch" and 3 cm "1 1/4 inch", but those are trade nicknames rather than conversions. 2 cm is actually 0.787 inch and 3 cm is 1.18 inch. Figures quoted against the nominal inch sizes come out roughly 6% heavy, which is enough to matter when you are sizing brackets.
A typical kitchen with 55 square feet of 3 cm granite therefore carries about 920 pounds (417 kg) of stone, spread across the cabinet runs. Standard cabinets handle this without modification, but unsupported overhangs beyond about 10 inches need corbels or steel brackets.
How the Calculation Works
Weight is simply volume multiplied by density. Convert every dimension to feet first, multiply them together for cubic feet, then multiply by 170:
Weight (lbs) = Length ft × Width ft × Thickness ft × 170
For an 8 ft × 2.5 ft countertop at 3 cm (0.0984 ft): 8 × 2.5 × 0.0984 × 170 ≈ 335 lbs, or about 152 kg. Divide by 2,000 for tons. To work directly in metric, multiply cubic metres by 2,723 instead. The same method works for other stone types by swapping the density — see the stone weight calculator for marble, slate, limestone and bluestone, or the stone slab weight calculator for slab-specific estimates.
Why Granite Weight Matters
Underestimating stone weight causes real problems. Second-floor and island installations may need the floor structure checked. Transport is limited by your vehicle's payload rating, not by whether the piece fits. And handling a 350-pound countertop safely takes at least three people plus suction cups — attempting it with two is how slabs crack and backs get injured.
Frequently Asked Questions
How much does granite weigh per cubic foot?
Granite weighs approximately 170 pounds per cubic foot, or about 2,720 kilograms per cubic metre. This makes it denser than limestone and sandstone (around 150 lbs per cubic foot) and similar to marble and travertine.
How much does a granite slab weigh?
A full 3 cm granite slab of about 50 square feet weighs roughly 900 pounds. A 2 cm slab of the same size weighs around 625 pounds. Individual countertop pieces cut from those slabs typically weigh 200-400 pounds each.
How much does granite weigh per square foot?
About 12.5 pounds per square foot at 2 cm thickness, 18 pounds per square foot at 3 cm, and roughly 28 pounds per square foot at 2 inches. Weight per square foot is directly proportional to thickness.
Can my cabinets support granite countertops?
Standard well-built cabinets support granite without modification, since the load spreads across the whole run. Overhangs are the exception: anything beyond about 10 inches unsupported needs corbels or steel brackets, and island or second-floor installations are worth having checked by a professional.
Is granite heavier than marble?
They are nearly identical. Both sit at roughly 170 pounds per cubic foot, so a granite and a marble slab of the same size weigh about the same. Quartzite is slightly heavier at around 172, and slate heavier still at about 175.
Sources & Methodology
This calculator uses standard published conversion factors and material densities. Density figures are typical values — actual material varies by quarry, moisture content and compaction, so treat results as estimates and confirm quantities with your supplier before ordering.
- Special Publication 811: Guide for the Use of the International System of Units — NIST
Defines the exact conversion factors between pounds, kilograms and other units used by this calculator.
- Publications and Documentary Standards (Handbook 44) — NIST Office of Weights and Measures
The specifications and tolerances for commercial weighing devices adopted by all 50 states.
- Weights, measures and packaging: the law — GOV.UK
UK rules on units of measurement, including the stone as a unit of body weight.
Reviewed by the Stone Calculator editorial team
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