How do I calculate countertop square footage?

Multiply the length by the depth of each run and add them: 3000 + 1800 + 900 mm at 620 mm deep is 3.53 m², or 38.0 sq ft. Add the upstand (height × length) if it is cut from the same stone.

How many slabs do I need for my countertop?

Lay the runs on the slab, longest first: the kitchen above fits on 1 slab of 3200 × 1600 mm. A veined stone may need one more to match the pattern.

How much does a quartz countertop weigh?

20 mm quartz weighs about 48 kg per m² and 30 mm about 72 kg per m²; granite is about 54 and 81 kg per m².

Countertop Calculator: Area, Slabs and Weight

Countertop calculator

A kitchen of 3000 + 1800 + 900 mm runs at 620 mm deep is 3.53 m² (38.0 sq ft) of worktop; in 20 mm quartz it weighs 170 kg and fits on 1 slab of 3200 × 1600 mm. Type each run as length × depth and the calculator adds the upstand, counts the slabs, the polished edge and the cut-outs, and prices the job if you give it your prices.

How it is worked out

area = Σ length × depth (+ upstand height × run length) weight = area × thickness (mm) × density (t/m³) kg slabs = pieces laid longest first on shelves along the slab, with the kerf between them edge = the front of every piece

For the kitchen above: (3.0 + 1.8 + 0.9) × 0.62 = 3.53 m². 20 mm quartz is 20 × 2.4 = 48 kg/m², so the worktop weighs 170 kg. A run longer than the slab is split into equal pieces and counted as a joint.

What this page does not do

It does not match the veining. On a marble or a veined quartz the fabricator lays the pieces out on the slab by eye, which can take another slab.
It does not template. Walls are rarely square: the final sizes come from the template taken on site.
It does not check the cabinets. A worktop of 150 kg or more needs a sound carcass and, over an overhang, supports.

Questions people ask

How do I calculate countertop square footage?: Multiply the length by the depth of each run and add them: 3000 + 1800 + 900 mm at 620 mm deep is 3.53 m², or 38.0 sq ft. Add the upstand (height × length) if it is cut from the same stone.
How many slabs do I need for my countertop?: Lay the runs on the slab, longest first: the kitchen above fits on 1 slab of 3200 × 1600 mm. A veined stone may need one more to match the pattern.
How much does a quartz countertop weigh?: 20 mm quartz weighs about 48 kg per m² and 30 mm about 72 kg per m²; granite is about 54 and 81 kg per m².