ConcreteCalc
PRO All 30 Tools
All 30 Tools

Garage Floor & Shed Slab Calculator

Calculate ready-mix concrete yardage for interior garage floors, detached workshop slabs, and equipment shed pads. Includes optional transitional exterior vehicle entrance ramps (aprons) and polyethylene vapor barrier coverage.

Interactive Garage Slab Calculator

ENGINEERING SCHEMATIC
Heavy-Duty Garage Floor Slab
Length (L) Width (W) Thickness (T: 4"–6") Surface Area = L × W
💡
Pro Contractor Recommendation: Use minimum 3,500 to 4,000 PSI concrete for garage floors to resist freeze-thaw spalling and vehicle deicing salts.
Garage Floor / Shed Pad Dimensions
Total Ready-Mix Concrete Required
11.41 cu yds
(308.0 cu ft / 8.72 m³)
Main Floor Area
576 sq ft
8.89 cu yds interior floor
Exterior Apron Ramp
1.48 cu yds
Door threshold vehicle ramp
Vapor Barrier Retarder
634 sq ft
10-mil poly with 10% overlap
Perimeter Formwork
96 lin ft
Lumber edge forms

Key Construction Details for Garage Slabs

Unlike simple patio slabs, garage floors must support heavy concentrated tire loads and protect against moisture migration:

  • Thickness: Minimum 4 inches for light storage sheds; minimum 5 to 6 inches for passenger cars, SUVs, and workshop equipment.
  • Vapor Barrier (10-Mil Polyethylene): Essential beneath the concrete to prevent groundwater vapor from condensing on the floor surface, which ruins epoxy coatings and causes tools to rust.
  • Exterior Entry Apron: A 3-to-4 foot sloped exterior ramp placed outside the garage door threshold to ensure smooth vehicle tire transition from grade.