Concrete calculator
How much concrete for a slab, patio or footing, and how many bags to buy.
How it works
Volume = length × width × thickness, + 10% waste. Dry mix weighs about 2,200 kg/m³ (a 25 kg bag ≈ 11.5 litres).
Results are for guidance only and do not replace professional advice.
Worked example
With the default values:
- Length (m)4
- Width (m)3
- Thickness (cm)12
- Ready-mix bag25 kg (≈ 11.5 L)
- Price per bag5.5
you get:
- Bags to buy138 × 25 kg
- Concrete volume1.44 m³ (1.584 m³ with 10% waste)
- Estimated cost€759.00
- Total weight3,450 kg
Frequently asked questions
How does the “Concrete calculator” tool work?
Volume = length × width × thickness, + 10% waste. Dry mix weighs about 2,200 kg/m³ (a 25 kg bag ≈ 11.5 litres).
What do I need to enter?
Just fill in: length, width, thickness, ready-mix bag, price per bag. The result updates as you type.
Can you give an example?
Length (m): 4; Width (m): 3; Thickness (cm): 12; Ready-mix bag: 25 kg (≈ 11.5 L); Price per bag: 5.5 → Bags to buy: 138 × 25 kg; Concrete volume: 1.44 m³ (1.584 m³ with 10% waste).
Is this calculator free, and is my data private?
Yes. HOD Calc is completely free with no sign-up. The calculation runs in your browser: nothing you type is sent or stored.