Concrete volume and bag calculator
How much concrete do I need and what will it cost?
Concrete volume is length × width × depth for a slab, or cylinder volume × count for round piers. Add your margin and divide litres by bag yield; cost uses your own bag price.
A slab has volume length × width × depth. A cylinder has volume π × (diameter ÷ 2)² × height. Multiply by identical casts and the selected margin. Multiply m³ by 1,000 and divide by the product’s litres of finished concrete per bag; round up to complete bags.
Worked example
The prices below are illustrative inputs, not market prices. Replace them with your quotes or store prices.
Length: 2 m; Width: 3 m; Depth / height: 0.1 m; Number of identical casts: 1. Geometric volume: 2 × 3 × 0.1 = 0.6 m³. Waste: 10% → volume including waste: 0.66 m³ = 660 l.
Concrete yield per bag: 12 l → 660 / 12 = 55 concrete bags. Price per concrete bag: 50 SEK → material subtotal: 2 750 SEK. Labor budget: 100 SEK; Delivery budget: 200 SEK → total budget: 3 050 SEK.
How many bags do four round piers need?
Choose cylinder, diameter 0.2 m, height 0.5 m and count 4. With a 10% margin and 12 litres of finished concrete per bag, buy 6 whole bags. These are example dimensions, not a pier design recommendation.
π × (0.2 / 2)² × 0.5 × 4 ≈ 0.062832 m³
0.062832 × 1.10 × 1000 ≈ 69.115 l; 69.115 / 12 ≈ 5.76 → 6
What is excluded from the material budget?
Bag yield means litres of finished concrete, not dry bag weight. Defaults are editable assumptions, not universal product values. The model does not specify concrete class, reinforcement, frost protection or load capacity. Check the chosen product sheet and project design; the bag price does not price separately ordered ready-mix.
Enter your own SEK prices per complete package or piece as labelled. Zero means that cost has not been budgeted. Labor and delivery are added separately.
Product instructions: Weber.
Planning an outdoor area too? Calculate separate materials with the paving calculator or deck calculator. This concrete quantity does not determine how their foundations should be designed.