Overview
Enter the foundation’s length, width, and height to convert the shape into concrete volume in cubic meters. Add a waste allowance if you want the result to include a reserve for spillage, uneven excavation, or minor overfill. The calculator also shows the side area of the foundation, which helps when ordering waterproofing, insulation boards, or protective coating. It is suitable for linear strips, isolated footings, and other simple rectangular foundation elements where a straight volume estimate is enough.
Use cases
- Strip foundation takeoffEstimate the concrete needed for a long, narrow strip before placing an order.
- Footing material listWork out the mix quantity for isolated footings under posts or columns.
- Waterproofing area planningMeasure the side area that needs membrane, coating, or damp-proofing.
- Bagged mix purchase checkConvert the cubic volume into a realistic number of sacks from the product yield.
- Insulation board planningSize the vertical foundation surfaces that will receive perimeter insulation.
How it works
- 1
Enter the foundation length in meters.
- 2
Enter the width in meters.
- 3
Enter the height in centimeters.
- 4
Set the waste allowance percentage.
- 5
Choose the concrete yield per bag if you are buying bagged mix.
- 6
Review the adjusted volume, bag count, and side area.
Examples
Strip foundation for an extension
Input: Length 14 m, width 0.45 m, height 70 cm, waste 8%, bag yield 0.02 m3
Output: Concrete volume: 4.75 m3. With waste: 5.13 m3. Bags: 257. Side area: 19.60 m2.
A typical narrow foundation around an extension footprint.
Pad footing under posts
Input: Length 2.4 m, width 0.8 m, height 40 cm, waste 5%, bag yield 0.025 m3
Output: Concrete volume: 0.77 m3. With waste: 0.81 m3. Bags: 33. Side area: 2.56 m2.
Useful when planning a small isolated footing with a known pour size.
Retaining wall base
Input: Length 9 m, width 0.6 m, height 90 cm, waste 12%, bag yield 0.03 m3
Output: Concrete volume: 4.86 m3. With waste: 5.44 m3. Bags: 182. Side area: 17.10 m2.
A stronger footing layout where the reserve helps cover losses during the pour.
FAQ
What dimensions should I enter for a stepped foundation?
Use the dimensions of the rectangular section only. If the foundation has steps or thickened edges, calculate each section separately and add the results.
Why is the side area useful if I already have the volume?
The volume tells you how much concrete is needed. The side area helps estimate the amount of waterproofing, coating, or insulation applied to the vertical faces.
Does the calculator account for reinforcement bars?
No. It estimates concrete, bag count, and side area only. Rebar must be measured from the structural design or bar schedule.
How do I choose the waste allowance?
Use a small reserve for neat excavations and a higher reserve if the trench is irregular, the formwork is complex, or the pour is difficult to control.
Can I use the bag count directly for purchase?
Use it as a buying estimate, not an exact count. Real bag usage changes with compaction, rounding of package yield, and site losses.