Home & DIY
Concrete calculator
Length × width × thickness → concrete volume and bags.
- Instant
- Free
- Private (processed locally)
- No sign-up
Calculate concrete for a slab
Enter length, width and thickness. The tool gives the volume in m³, in liters and the number of 25 kg bags (≈ 12.5 L per bag).
The formula
- Volume (m³) = L × W × (thickness cm ÷ 100)
- Liters = volume × 1000
- Bags = volume ÷ 0.0125 (rounded up)
- Suggested margin: +5–10%
Example
| Input | Value |
|---|---|
| Dimensions | 3 m × 2 m × 10 cm |
| Volume | 0.6 m³ |
| Liters | 600 L |
| 25 kg bags | ≈ 48 |
Estimate: the real yield per bag varies by product. 100% local calculation.
Frequently asked questions
How do I calculate concrete volume?
Volume (m³) = length × width × thickness, all in meters. Convert thickness in cm to meters (÷100). E.g. 3 × 2 × 0.10 = 0.6 m³.
How many 25 kg bags?
A 25 kg bag of ready-mix concrete yields about 12.5 L (0.0125 m³). So 0.6 m³ needs ≈ 48 bags.
Should I add a margin?
Yes, add 5–10% for waste, settling and formwork irregularities. The tool rounds the number of bags up.
What thickness for a slab?
A patio slab is often 8–12 cm; a load-bearing slab is thicker. Follow your project’s requirements.