Concrete Bags Calculator
Estimate bags of premixed concrete from volume and product yield.
What this tool calculates
Estimate bags of premixed concrete from volume and product yield. The main inputs on this page are Concrete required (m³), Yield per bag (litres), Extra allowance (%). The result is intended to be readable immediately, with the explanation below available when you need to verify the method.
Method and calculation basis
Concrete volume is geometric volume. Rectangular pours use length × width × depth; circular pads use πr² × depth; round columns use πr² × height; rings subtract the inner cylinder from the outer cylinder. Waste allowance is applied after the base volume.
Worked examples
Rectangular slab
6 m × 4 m × 0.10 m = 2.40 m³; with 10% extra, order basis becomes 2.64 m³.
Round pad
2 m diameter × 0.15 m depth gives π × 1² × 0.15 ≈ 0.471 m³.
Understanding the result
The output should be read in the units shown beside the result. If you are comparing alternatives, keep all unchanged assumptions identical and alter one input at a time. That makes it easier to see which value is responsible for the difference.
Assumptions, edge cases and accuracy
This is a quantity or geometry estimate, not structural design approval. Product yield, compaction, joints, substrate condition, reinforcement, waste and site tolerances can materially change the amount required.
Sources and methodology
- BSI / applicable British Standards — Relevant construction measurement and design standards where applicable
- Manufacturer technical data — Product coverage, yield, density and installation requirements
Method reviewed for Instant Solvers V10.0 · October 2026. If you find a calculation or explanation that needs correcting, use the site Contact page and include the tool URL and the values you entered.