Foundation Calculator
Calculate the volume of concrete required for slab, strip, or footing foundations, with configurable dimensions and waste margins.
Calculation Results
Total estimated concrete volume in cubic yards.
Total estimated concrete volume in cubic meters.
How This Calculator Works
To estimate foundation concrete requirements:
- Select the foundation configuration (Slab, Strip/Trench, or Pier Footings).
- Specify the dimensions (length, width, depth, or diameter as requested).
- For footings, provide the number of posts and whether they are square or round.
- Enter a waste buffer factor to cover spillage or uneven excavation floors.
Formula & Calculations
Concrete volume formulas vary based on the foundation style selected:
- Slab Foundations:
Volume = Length × Width × Depth - Strip Foundations: Trench concrete runs around the slab perimeter.
Volume = 2 × (Length + Width) × Trench Width × Depth - Square Footings:
Volume = Footings Count × Length × Width × Depth - Round Pier/Sonotubes:
Volume = Footings Count × π × (Diameter / 2)² × Depth
All equations incorporate the user-specified waste buffer margin (typically 10%).
Step-by-Step Calculation Examples
Standard Slab Foundation (30ft x 24ft x 6in depth)
Calculating pour requirements for a residential garage slab foundation with a 10% waste buffer.
- foundation_type: slab
- length: 30
- width: 24
- depth: 6
- waste: 10
- volume: 14.67 cu yd
- volume_m3: 11.21 cu m
Frequently Asked Questions
How deep should a concrete slab foundation be?
Standard residential concrete slabs for garages or sheds are typically 4 to 6 inches thick. Load-bearing structures or heavy vehicles usually require 6 inches of concrete with rebar reinforcement.
What is a strip foundation?
A strip foundation (or trench footing) is a continuous band of concrete running underneath load-bearing masonry walls to distribute the building weight evenly over the soil.
How much waste should I allow for concrete foundations?
A standard allowance is 10%. Concrete pours involve slight spillage, and trench digs are rarely perfectly flat or straight, which consumes extra volume.
Can I use Sonotubes for footing foundations?
Yes. Sonotubes are cardboard forms used to cast cylindrical concrete columns (pier footings) below ground level. You should choose the "Pier Footings" options with "Round Pier" shape.
What strength concrete is needed for footings?
Typically, residential code specifies concrete with a minimum compressive strength of 3,000 PSI (pounds per square inch) for footings and columns.