What this calculator does
Turn slab dimensions into an ordering quantity, then compare alternative dimensions before discussing the order with a supplier. Metric inputs use metres for length and width and centimetres for thickness. US inputs use feet and inches. This is a material estimator, not an engineering design.
Formula, assumptions and sources
Net cubic metres = length × width × thickness after conversion. 1 ft = 0.3048 m; 1 in = 0.0254 m. Ordered volume = net volume × (1 + allowance / 100). Cubic yards = cubic metres ÷ 0.764554857984. Price applies per m³ in Metric or per yd³ in US customary. This estimates rectangular slab volume, not structural suitability or a mix design.
Worked example
This example uses the initial values shown in the form. It is illustrative and is not a saved personal result.
Example inputs
- Measurement system
- Metric
- Length (m or ft)
- 5
- Width (m or ft)
- 4
- Thickness (cm or inches)
- 10
- Extra material allowance (%)
- 10
- Currency
- USD
- Price per purchase unit (optional)
- 0
Example result
These are alternative totals, not quantities to add together.
View chart data
| Item | Value |
|---|---|
| Net slab | 2 |
| With allowance | 2.2 |
Material only; excludes delivery, labour and tax. A zero price means cost has not been entered. Confirm supplier ordering increments, thickness and specifications before ordering.
Frequently asked questions
Does this determine safe slab thickness?
No. Thickness, reinforcement, ground conditions and load requirements need suitable project specifications.
Does the volume include extra material?
The net volume excludes extra material. The ordering values include your chosen allowance; suppliers may apply minimum quantities and rounding.
Method and example checked 4 November 2026. How we check calculations