Check the path
Your calculation audit
Every total is shown as a short sequence so you can see what was measured, deducted, adjusted and rounded.
- 01Awaiting valid measurementsComplete the fields above to reveal the formula path.
Walls & Masonry
Concrete & screed calculator
Estimate concrete or screed volume from a rectangular pour, with practical bag rounding.
Transparent formulaFormula v1.0 · length × width × depth × waste allowance
Scope boundary: Materials estimate only — not for foundations, footings, load-bearing work or structural design.
Measure clearly
Simple guidance
Measure the inside length and width of the rectangular pour. Use the finished depth, not the depth of a trial hole or uneven ground.
Worked example
Follow the same logic
A 3 m × 2 m slab at 100 mm deep is 0.6 m³ before the selected waste allowance. The bag total is a purchase estimate, rounded up.
Planning tipWrite down the product factor or pack size you used, so a later change is easy to trace.
Before you buy
Three quick checks
- 01
Use the intended finished depth across the full pour.
- 02
Check whether the supplier quotes bag yield or mixed volume.
- 03
Treat the result as material planning, not a structural specification.
Quick answers
Useful to know
Which depth should I enter?
Enter the finished pour depth that the project calls for. This calculator does not decide slab, footing or foundation depth.
Can I order from the bag estimate?
Use it as a planning quantity, then check the exact yield, product instructions and pack availability before buying.
Review record
Transparent, source-ready method
Last reviewed: 15 October 2026. Formula version: v1.0. Source/review data to be added — Calculator.Shop does not present placeholder figures as an authoritative trade specification.