Concrete Shed Foundation Calculator
A 10×12 ft shed foundation at 4 inches thick requires 1.48 cubic yards of concrete — about 74 bags of 80-lb mix, manageable as a weekend DIY project. Enter your shed dimensions for exact volume, bag count, and material cost.
Pro Tips
- →Shed pads typically need 4 inches of concrete
- →Make the pad 6-12 inches larger than your shed footprint
- →Include wire mesh reinforcement for crack prevention
- →Ensure proper gravel base and compaction
- →Level the site carefully before pouring
Includes 10% waste factor
That's typically a professional pour. See costs ↓
4 short emails from Dave: what a fair quote should land at for your slab, the scope changes that swing it ±$500, and whether DIY is actually cheaper at your volume. Reply anytime — he'll review your real quote.
Cost Estimate
Estimated material costs for your project
Recommendation: Ready-Mix Concrete
For projects over 1 cubic yard, ready-mix is typically more economical and easier to work with.
74 bags × 80lb
1.63 cubic yards + delivery
120 sq ft × $3.00–$8.00/sq ft
Prices vary by location and time. Contact local suppliers for accurate quotes.
For general step-by-step instructions, read our complete How Thick Should Concrete Be and When To Use Rebar.
Shed Foundation Concrete: What You Need to Know
A concrete shed pad is one of the most beginner-friendly concrete projects. The math is simple, the form is rectangular, and the quantities are small enough that bagged concrete is usually practical.
Concrete Needed by Shed Size
| Shed Footprint | Pad Size (6" overhang) | Thickness | Cubic Yards | 80-lb Bags |
|---|---|---|---|---|
| 6×8 ft | 7×9 ft | 4 in | 0.78 cu yd | 35 bags |
| 8×10 ft | 9×11 ft | 4 in | 1.22 cu yd | 55 bags |
| 10×12 ft | 11×13 ft | 4 in | 1.63 cu yd | 74 bags |
| 12×16 ft | 13×17 ft | 4 in | 2.54 cu yd | 115 bags |
| 14×20 ft | 15×21 ft | 4 in | 3.63 cu yd | ≥163 bags — use ready-mix |
All quantities include 10% waste buffer. Pad sizes extend 6 inches beyond shed footprint on each side.
Why Make the Pad Larger Than the Shed?
Standard practice is to extend the slab 6–12 inches beyond the shed walls on all sides:
- Prevents water from pooling directly against the shed base
- Gives you a clean walkway surface around the door
- Easier to install shed anchors without hitting the slab edge
- Looks finished rather than having grass right up to the wall
For a 10×12 shed: pour a 12×14 pad (or 11×13 minimum).
Thickness: 4 Inches Is Standard
Most residential sheds need a 4-inch slab:
- Standard storage shed: 4 inches
- Workshop with power tools and equipment: 5 inches
- Drive-in access or heavy machinery (tractors, ATVs): 5–6 inches
- Very large shed (over 200 sq ft) on soft soil: 5 inches + wire mesh
Each additional inch adds roughly 25% more concrete volume.
Gravel Base Is Non-Negotiable
A 4–6 inch compacted gravel base under the slab prevents three common problems:
- Drainage: Water drains away rather than pooling under the slab
- Frost heave: Gravel reduces the moisture available for freeze-thaw movement
- Settling: Compacted crushed stone provides a stable bearing surface
Skipping the gravel base is the most common cause of shed slab cracking and settling. Budget 1–1.5 tons of crushed stone for a 10×12 pad.
For full cost estimates including labor, see the concrete shed base cost calculator.