How to use the Concrete Calculator
- Choose the measurement system and measure the slab inside the forms.
- Enter length, width, depth, and a practical waste allowance.
- Order using the total volume and confirm supplier minimums and mix requirements.
How the calculation works
Volume = length × width × depthDimensions are converted to meters before multiplication. Waste is added to the base volume. Bag count uses an approximate yield of 0.01699 m³ per 80 lb premixed bag.
Example calculation
A 5 m × 4 m slab at 10 cm depth has a base volume of 2.00 m³. Adding 10% gives 2.20 m³, approximately 2.88 cubic yards.
How to interpret the result
The estimate covers a rectangular slab. Irregular shapes should be divided into simpler sections and added together.
Notes and assumptions
- Dimensions describe the filled interior volume.
- Bag yield varies by product and mixing conditions.
- Subgrade, reinforcement, delivery minimums, and structural design are excluded.
Common questions
Concrete Calculator questions
How much waste should I add?
Five to ten percent is common for simple work, but site conditions and supplier guidance should determine the allowance.
Does it calculate ready-mix orders?
Use the total cubic-meter or cubic-yard result when requesting a supplier quote.
Can I calculate several slabs?
Calculate each shape separately and add their total volumes.