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How to Calculate Concrete Volume

Calculating concrete volume accurately avoids the waste and cost of over-ordering or the delay and patching required if you run short. Concrete is ordered or purchased in cubic metres (m³) or cubic yards. For small jobs, pre-mixed bags are convenient — one 60 kg bag of concrete mix typically yields about 0.028 m³ (28 litres) of concrete.

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Formula

$$Volume\ (slab) = Length \times Width \times Thickness$$

Concrete Volume Calculator

Calculate the volume of concrete needed for a slab, footing, or column.

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Worked Example

Given:

Shape = Slab / RectangleLength = 4 mWidth = 3 mThickness = 0.1 m (100 mm)
ResultVolume: 1.2 m³ — 60kg Bags Needed: 43 bags

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FAQs

How much does concrete weigh?

Standard concrete has a density of approximately 2,400 kg/m³. One cubic metre of concrete weighs about 2.4 tonnes. Pre-mixed 60 kg bags contain dry ingredients — adding water increases weight slightly and yields approximately 0.028 m³ of cured concrete per bag.

Should I order extra concrete?

Always add 5–10% extra to your calculated volume to account for wastage, spillage, slight variations in forms, and uneven ground. Running short mid-pour is a serious problem as concrete must be placed and finished continuously. Having a small amount left over is preferable to stopping and creating a cold joint.

What mix ratio should I use for different applications?

For footings and foundations: 1:2:4 (cement:sand:aggregate) or C20 mix. For slabs: 1:1.5:3 or C25 mix. For driveways: C30 mix or stronger. For structural work: always consult an engineer. Pre-mixed bags specify the application on the packaging. Adding too much water weakens the concrete significantly.