How much concrete do I need for a 10m × 10m slab?

A 10m × 10m slab covers 100 square metres. At 100 mm thick that is 10.00 cubic metres of concrete, or 11.00 once you add the usual ten percent for waste. At 150 mm — the thickness you want if a vehicle will use it — it rises to 15.00 cubic metres, 16.50 with waste. Thickness scales the volume linearly, so half again the depth is half again the concrete.

How many bags of concrete for a 10m × 10m slab?

About 1,000 bags of 25 kg at 100 mm thick, on the basis that a 25 kg bag yields roughly 0.01 cubic metres of finished concrete. That figure alone answers the bags-or-truck question: mixing that many by hand is well beyond a single day of work, and ready-mix will be cheaper as well as faster.

How many ready-mix loads for a 10m × 10m slab?

2 loads at 100 mm thick, assuming an eight cubic metre truck. More than one load means the joint between them matters: either the next truck is on site before the first finishes, or the pour stops at a planned construction joint with reinforcement carried through. A gap long enough for the first concrete to stiffen leaves a cold joint, which is a permanent weak plane.

What is a 10m × 10m slab usually for?

Barn, sports base or commercial floor. That matters for the specification rather than the quantity: the area gives you the concrete, but what sits on the slab decides the thickness, whether it needs reinforcement, and how good the sub-base has to be. Change the thickness on the calculator above to see the volume move — it is the input that costs the most and gets the least thought.

How far apart should control joints be?

No more than about twenty-four times the slab thickness, and with panels kept near square. On a 100 mm slab that gives 2.4 metres; at 150 mm it gives 3.6. The shape rule matters as much as the spacing: a panel much longer than one and a half times its width behaves like a beam and cracks across its middle, so a long slab should be jointed on a grid rather than in strips.

Do I need a damp-proof membrane?

Under anything with a floor people occupy, yes. A concrete slab is not waterproof — moisture wicks up through it by capillary action and appears as damp flooring, lifting adhesive, or condensation on whatever is stored on it. A polythene membrane under the slab stops that. For an outdoor slab such as a patio or yard it is unnecessary, since the surface is exposed anyway and trapped moisture has nowhere useful to go.

How much sub-base does a slab need?

A hundred millimetres of compacted granular material under a domestic slab, a hundred and fifty under anything carrying vehicles, and more on soft or made-up ground. Order it by the loose volume rather than the finished depth, because crushed stone settles by roughly a quarter as it compacts. Compact it in layers of no more than a hundred millimetres — a single deep dump never consolidates properly and the slab settles into the soft spots later.

Does a slab need reinforcement?

It depends on what the slab carries and what it sits on. A small shed base on firm ground genuinely does not need it. Anything carrying vehicles does, and so does any slab on ground that may move — recent excavation, made-up ground, near trees. Reinforcement does not prevent cracking; it holds the pieces together across a crack so it stays tight rather than opening into a trip hazard or a water path.

Under about half a cubic metre, bags are simpler and there is no minimum charge. Above roughly a cubic metre, ready-mix wins on cost as well as effort once you count the delivery and short-load charges honestly. There is also a quality argument that matters more than the money: a slab poured continuously from one load is monolithic, while one built up from batches mixed over several hours has cold joints running through it that you cannot see and cannot repair.

Concrete for a 10m × 10m Slab

A hundred square metres is a round number that turns up constantly in quotes and estimates, which is useful, because it makes a good yardstick. At a hundred millimetres it is ten cubic metres of concrete; at a hundred and fifty it is fifteen. Whatever your actual slab, working out how it compares to a hundred square me...

SLAB DIMENSIONS

LENGTH (metres)

WIDTH (metres)

THICKNESS (millimetres)

CONCRETE PRICE ($/m³, optional)

Enter your local ready-mix price for an estimate.

RESULTS

VOLUME (exact)

10.00 m³

WITH 10% WASTE — order this amount

11.00 m³

25 KG BAGS

1000

≈ 0.01 m³ per 25 kg bag

ESTIMATED MATERIAL COST

$1,650

at $150/m³ + 10% waste

SLAB VISUALISER (not to scale)

SLAB SUMMARY

Surface area100.00 m²

Thickness100 mm

Volume exact10.0000 m³

Volume +10%11.0000 m³

25 kg bags1000 bags

THICKNESS GUIDE

75mm

Paths, light paving

Foot traffic

100mm

Patios, residential slabs

Standard residential

150mm

Driveways, garage floors

Vehicles

200mm

Commercial floors

Heavy loads

UNIT CONVERSIONS

1 cubic yard = 27 cubic feet

1 cubic yard ≈ 0.765 m³

80 lb bag ≈ 0.6 cubic feet

60 lb bag ≈ 0.45 cubic feet

25 kg bag ≈ 0.01 m³

Always order 10% extra for waste

Created with❤️byeaglecalculator.com

HOW TO USE

1
The calculator opens with 10 by 10 metres already entered. Adjust the thickness to match what the slab will carry — 100 mm for a pedestrian floor, 150 mm where a vehicle will use it.
2
Read the volume with and without the ten percent waste allowance. Order the figure with waste included; the exact figure is there so you can see how much of the order is margin.
3
Compare the bag count against the ready-mix load count. At 10.00 cubic metres this is past the point where bags make sense on cost or effort.
4
Switch to imperial with the unit toggle if you are working in feet and inches, or change the dimensions if your slab is not exactly 10m × 10m.

WORKED EXAMPLE

A 10m × 10m slab at 100 mm thick. The area is 10 × 10 = 100 m². Multiplying by the 0.1 m thickness gives 10.00 m³ of concrete. Adding ten percent for waste — for an uneven sub-base, spillage, and the last of the load left in the chute — brings the order quantity to 11.00 m³. That is about 26.4 tonnes. In 25 kg bags, at roughly 0.01 m³ of finished concrete per bag, that is 1,000 bags. From a truck holding 8 m³ it is 2 loads. At 150 mm instead, the same area needs 15.00 m³, or 16.50 m³ with waste — half again the concrete for half again the depth.

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Last updated: July 28, 2026 · Formula verified by EagleCalculator team · Eagle-eyed accuracy for every calculation.