Concrete Calculator
Estimate concrete volume and pre-mixed bag requirements for slabs and footings
How to Use This Calculator
- Enter the total Length (m) of the concrete slab or trench.
- Specify the total Width (m) of the area.
- Provide the required Thickness / Depth (cm) of your concrete pour.
- Select the standard pre-mixed concrete bag weight available in your area.
- Click “Calculate Requirements” to estimate cubic volume, total weight, and bag count including safety margin.
The Formula Used
Volume is derived using standard rectangular dimensional geometry converted to cubic meters, plus a recommended 10% waste buffer:
Total Weight (kg) = Volume (m³) × 2,300 kg/m³ (Average Wet Density)
Estimated Bags = ( Total Weight / Bag Weight ) × 1.10 (10% Buffer)
Frequently Asked Questions (FAQ)
How much area does one bag of pre-mixed concrete cover?
A standard 25 kg bag yields roughly 0.011 cubic meters of mixed concrete, covering about 0.11 m² at a depth of 10 cm.
Why is a 10% extra margin added to the concrete total?
An extra 10% compensates for uneven ground surfaces, excavation spillage, formwork expansion, and mixing losses.
How heavy is mixed concrete per cubic meter?
Standard cured concrete weighs approximately 2,300 to 2,400 kilograms per cubic meter depending on aggregate density.
When should I order ready-mix trucks instead of pre-mixed bags?
For pours exceeding 1.5 to 2 cubic meters, ordering premixed concrete trucks is generally more cost-effective and labor-efficient.
How long should concrete cure before bearing heavy weight?
Concrete reaches ~70% of its ultimate strength after 7 days and full structural strength after 28 days of proper curing.