Countertops, hearths, steps, flagstones and wall cladding are heavy. A 3 cm granite worktop weighs about 80 kg per square metre, so cabinets, floors and walls need to be checked before installation. This calculator finds the weight of rectangular, round or triangular slabs of natural stone or concrete.
How to use the Stone Weight Calculator
- Material
- Custom density
- Shape
- Length (or diameter)
- Width
- Thickness
- Quantity
- Every result field is editable: type into Weight of one piece or any other result and Thickness plus every other field update to match.
Results update as you type, and every field accepts the units shown in its menu.
How it works
The calculator finds the face area of the shape, multiplies by the thickness for the volume and by the material density for the weight. The weight per unit area is handy for checking floor, shelf or wall loads.
Densities used
| Material | kg/m³ | lb/ft³ | kg/m² per mm |
|---|---|---|---|
| Granite | 2,700 | 168.6 | 2.70 |
| Marble | 2,700 | 168.6 | 2.70 |
| Limestone | 2,611 | 163.0 | 2.61 |
| Sandstone | 2,300 | 143.6 | 2.30 |
| Slate | 2,800 | 174.8 | 2.80 |
| Basalt | 3,000 | 187.3 | 3.00 |
| Quartzite | 2,650 | 165.4 | 2.65 |
| Concrete | 2,400 | 149.8 | 2.40 |
| Flagstone (sandstone) | 2,400 | 149.8 | 2.40 |
Tips for an accurate estimate
- Sketch the job and split irregular areas into rectangles, circles and triangles before you measure.
- Add a waste allowance – typically 5–10% for simple layouts and 15–20% for diagonal, curved or heavily cut work.
- Check the coverage or yield printed on the product, because sizes and densities vary between manufacturers.
- Buy all units of a finished material (tile, brick, siding) from the same batch so colours match, and keep a few spares for repairs.
- Confirm local prices – quarry, lumber and steel prices vary widely by region and season.
Common mistakes to avoid
- Ordering exactly the calculated amount with no allowance for breakage, offcuts and settlement.
- Forgetting to subtract doors, windows and other openings – or subtracting small ones that still need cutting around.
- Confusing US short tons (2,000 lb) with metric tonnes (1,000 kg) when comparing quotes.
Inputs explained
| Field | What to enter |
|---|---|
| Material | Choose one: Granite, Marble, Limestone, Sandstone … |
| Custom density | Units: kg/m³, lb/ft³, g/cm³, lb/yd³ |
| Shape | Choose one: Rectangle / square, Circle (length = diameter), Right triangle |
| Length (or diameter) | Units: m, ft, cm, in, yd |
| Width | Units: m, ft, cm, in, yd |
| Thickness | Units: mm, in, cm |
| Quantity | A number |
Formula
Weight = area × thickness × density × quantityArea: rectangle L × W, circle π D² ÷ 4, triangle L × W ÷ 2Worked example
Inputs — Material: Granite; Custom density: 2,700 kg/m³; Shape: Rectangle / square; Length (or diameter): 3 m; Width: 0.65 m; Thickness: 30 mm; Quantity: 1.
Results — Area of one piece = 1.95 m²; Volume of one piece = 58.5 L; Weight of one piece = 157.95 kg; Total weight = 157.95 kg; Weight per unit area = 81 kg/m².
Frequently asked questions
How much does a granite countertop weigh?
About 18–20 lb/ft² for 3 cm (1¼ in) slabs and 12–13 lb/ft² for 2 cm slabs.
How heavy is a marble slab?
Similar to granite: around 2,700 kg/m³, so 2 cm marble is 54 kg/m².
Is quartz countertop heavier than granite?
Engineered quartz (≈ 2,400 kg/m³) is a little lighter per volume but often sold thicker.
What formula does the Stone Weight Calculator use?
Weight = area × thickness × density × quantity.