Concrete calculator
Concrete volume for a slab, a strip or columns, with an allowance.
Fill in the fields and the result will appear here automatically.
Calculates geometric volume for a slab, rectangular strip or equal columns with a supplied section area. Net volume and your chosen allowance are separate. The page does not design a mix, concrete grade, reinforcement, load capacity or delivery conditions; you choose the allowance.
How it works
Formula and logic
Slab: V=L·B·t; strip: V=P·b·h; columns: V=S·H·n. Linear dimensions are in m, S in m² and volume in m³. n is a positive safe integer; active dimensions are positive and finite. Total is V·(1+w/100), separate allowance V·w/100, with w from 0 to 50%. Other shapes’ inactive dimensions are ignored.
Example
A 6 × 4 m slab 0.2 m thick is 4.8 m³ net; with a 5 % allowance you order 5.04 m³.
Fields and units
- Pour shape — list option
- Slab length — m
- Slab width — m
- Slab thickness — m
- Strip length — m
- Strip width — m
- Strip depth — m
- Column section area — m²
- Column height — m
- Number of columns — unitless
- Allowance — %
How to use
- — Choose the pour shape.
- — Enter its dimensions.
- — Set the allowance for losses and read the volume to order.
Method and limitations
- Calculation method
- Formula and logic
- Limitation
- The page does not design a mix, concrete grade, reinforcement, load capacity or delivery conditions; you choose the allowance.
FAQ
What allowance should I use?
Allowance is your input from 0 to 50%, not a prescribed minimum. Assess losses and geometric variation for the actual work; the calculator does not determine them.
Why is the net volume shown separately?
Because they are different numbers: the net volume checks the geometry, the other is what you order. Confusing them is a reliable way to run short on the last cubic metre.
How is this different from the strip foundation calculator?
This page has three simple geometries. Strip mode uses total strip length and a constant section; intersections and unequal segments need separate geometric accounting.
Is reinforcement accounted for?
No. Full geometric volume is used; reinforcement, inserts and voids are not automatically subtracted. Their share is not assumed universally negligible.