How to use the concrete slab calculator
This calculator helps you estimate concrete volume, bags and net mesh coverage for a slab. It is intended for quantity takeoffs, early budgets and checks against a measured schedule. Start with the dimensions or quantities for one clearly defined item of work. Enter values in the units shown beside each field; millimetres and metres are not interchangeable.
Mesh area is net plan area for one layer. It excludes overlaps, cutting loss and additional reinforcement. Bag yield depends on the product; check the supplier data.
Worked example
A 6 m × 4 m slab at 150 mm thick contains 3.6 m³ and has 24 m² of net mesh coverage per layer.
Before you order
Compare the result with your drawings and supplier information. Keep the original net quantity separate from allowances, and round purchasing quantities only at the ordering stage. Check whether delivery, labour and related materials belong elsewhere in your estimate. If the drawing or specification changes, update the inputs and record the revised basis instead of reusing an earlier total.
For the concepts behind this calculation, read Rebar (Reinforcement Steel), Damp Proof Membrane (DPM), Wastage Factor.
Common questions & estimating checks
What formula does the concrete slab calculator use?
Volume = length × width × thickness; mesh area = length × width — all calculations run directly in your browser using the exact inputs entered above.
How do you calculate a worked example?
A 6 m × 4 m slab at 150 mm thick contains 3.6 m³ and has 24 m² of net mesh coverage per layer.
What should be checked before ordering or pricing?
Verify dimensions against approved drawings, check supplier product yields and pack sizes, and keep net measured quantities separate from wastage or commercial risk allowances.