How Much Concrete Does Your Slab Need? Working It Out on the Tablelands

Short answer: multiply the length by the width to get the area in square metres, then multiply that by the thickness in metres to get the cubic metres of concrete. A 10 by 6 metre slab at 100 mm is 6 cubic metres. Our free calculator does the sum for you, and Shane checks every measurement on site before the pour.

Why the number matters before you call

Most people ring a concreter with a rough idea: a shed slab out the back, a new driveway, a pad for the water tank. Knowing the size in square metres and cubic metres turns that rough idea into something real. You can compare quotes on the same job, you know roughly how big the pour is, and the first conversation gets straight to the useful part.

It also helps you plan the space. Change the width by a metre and the volume moves more than most people expect, so it is worth playing with the numbers before you lock in a size.

The sum: length, width, thickness

There are only three measurements, and two of them you can take with a tape measure on the weekend.

• Length and width, in metres. Peg out the corners with string and measure the sides. Multiply them together and you have the area in square metres (m²).
• Thickness, in millimetres. This depends on the job and the loads, and it is the one Shane sets for you.
• Convert the thickness to metres. 100 mm is 0.1 m, 125 mm is 0.125 m, 150 mm is 0.15 m.
• Multiply the area by the thickness in metres. That gives you the cubic metres (m³) of concrete.

Concrete is ordered and quoted by the cubic metre, which is why that last number is the one that counts.

Worked examples

Here is how the sum plays out on a few common Tablelands jobs:

• A hobby shed, 6 x 6 m at 100 mm. 36 m² of slab, 3.6 m³ of concrete.
• A shed or garage slab, 10 x 6 m at 100 mm. 60 m² and 6.0 m³.
• The same 10 x 6 m slab at 150 mm. Still 60 m², but 9.0 m³. Half again as much concrete, just from the extra thickness.
• A bigger shed or machinery pad, 12 x 6 m at 150 mm. 72 m² and 10.8 m³.

That 100 versus 150 mm jump is the one to notice. The slab looks the same from the top, but the volume, and what holds it up under load, is very different.

How thick should the slab be?

On our slabs page we give the usual ranges: house slabs are typically 100 to 125 mm with engineered reinforcement, and shed slabs are often 100 to 150 mm, depending on the loads. A slab that only ever sees a ride-on mower is a different job from one that carries a loaded truck or farm machinery.

So use the range to get a feel for the volume, then let us set the real number. Shane confirms the right thickness for your job on site, and on an engineered house slab the plans set it. Tablelands soils move and the wet season hits hard, so the spec is matched to your ground and your loads, never guessed.

Use our calculator

We built a free "How much concrete is it?" calculator into our slabs and driveways pages so you do not have to do the sum on the back of an envelope.

• pick the closest job
• slide in the length and width, or type them into the boxes
• choose 100, 125 or 150 mm
• read off the area in m² and the volume in m³, with a slab drawing that fills as you go

There are no prices in it and nothing to sign up for. When the size looks right, hit "Get a quote for this slab" and it takes you to our quote form with the size, thickness and cubic metres already filled in, so we start the conversation with your numbers.

What the calculator does not cover

The calculator works out the slab itself. Shane still comes out, measures and confirms everything on site before anything gets poured.

That on-site visit is where the things a tape measure cannot tell you get sorted: the ground, the access for the truck and pump, the reinforcement, the right mix for the job and where the water will go in a storm. It is free, and you get a quote back within 48 hours.

If you have engineered plans, send them through. If you just know the size, tell us that. Either way works.

We pour slabs, driveways, sheds and decorative concrete across the Atherton Tablelands, from a 6 x 6 hobby shed to a full machinery pad on a dairy property, in Malanda, Atherton, Yungaburra, Tolga, Herberton, Walkamin, Peeramon, Millaa Millaa, Ravenshoe and Mareeba.

Frequently asked questions