Pergola Post Concrete Calculator — Bags Per Footing
Calculate concrete bags for pergola support posts in 4×4, 6×6, and 8×8 wood and metal post sizes. Returns 60 and 80-pound bag counts per post.
Enter Dimensions
Typically 1/3 of post height above grade
Results
Bags per Post
5bags
Total Bags
50bags
Volume per Hole
1.909cu ft
Concrete per post hole
Total Volume
19.09cu ft
All post holes combined
Editorial Standards
Each calculator is reviewed for formula accuracy, unit consistency, and alignment with current U.S. building practices before publication. We verify outputs against published engineering references and real-world project data. Learn more about our methodology.
Pergola posts carry vertical timber load and resist lateral wind force. Both are modest for typical residential pergolas, but the post depth and concrete volume should still meet fence-post standards (1/3 below grade, below frost line) to prevent leaning over time.
Use this calculator for free-standing pergola post estimation. For attached pergolas (one side bolted to the house), reduce the post count by half — the ledger board carries that side.
How to Pour Pergola Post Footings
Concrete per post (cu ft) = π × (Hole D ÷ 24)² × Depth × 12 − (Post Width ÷ 12)² × Buried Depth × 12.
Pergola Post Reference
- 4x4 small pergola, 10″ × 30″ hole: 1.10 cu ft = 2 bags 80 lb per post.
- 6x6 typical pergola, 12″ × 36″ hole: 2.10 cu ft = 4 bags 80 lb per post.
- 6x6 cold climate, 14″ × 48″ hole: 3.20 cu ft = 6 bags 80 lb per post.
- 8x8 large pergola, 16″ × 42″ hole: 4.16 cu ft = 7 bags 80 lb per post.
- Typical 4-post pergola (6x6): 16 bags total + ~$60-90 for concrete.
Frequently Asked Questions
How much concrete per pergola post?
For a 6×6 cedar pergola post in 12 inch × 36 inch hole: 2.10 cu ft = 4 bags of 80 lb. For 4×4 posts: 10 inch × 30 inch hole = 1.10 cu ft = 2 bags 80 lb.
What size posts for a pergola?
4×4 for small structures (under 8×8 ft, freestanding). 6×6 for typical residential pergolas (8×10 to 12×16 ft). 8×8 for large pergolas, those with heavy timber rafters, or those carrying vines/canopy weight.
How deep should pergola posts go?
36 inches minimum for 6×6 posts. 30 inches for 4×4. Below local frost line in cold climates. The taller the pergola, the deeper the post; an 8 ft tall pergola needs at least 32 inches buried (1/3 rule).
Should pergola posts have rebar?
Optional but recommended for larger pergolas (8×8 posts or 12+ ft spans). A single vertical #4 bar through the center of the concrete + a J-bolt at the top for the post anchor improves rigidity in high-wind conditions.
Can I attach a pergola to the house?
Yes — attached pergolas use only 2 posts at the outer corners + a ledger board attached to the house. Reduces post count and concrete requirements by 50%.
Looking for the general calculator?
Calculate how many bags of concrete you need per fence post hole. Supports 4×4 and 6×6 wood posts plus metal pipe posts in standard hole sizes.
Open the Concrete Fence Post Calculator: Bag Count →