Pergola Calculator
Plan your pergola build with a complete material list. Enter your desired dimensions and spacing to get exact counts for posts, beams, rafters, purlins, and hardware — plus post hole concrete and cost estimates.
Enter Pergola Dimensions
Full Material List
Posts (6×6)
Beams (2×10)
Rafters (2×8)
Rafter Length
Purlins (2×2)
Post Base Hardware
Post Hole Concrete (80 lb bags)
Total Board Feet
How to Use This Calculator
- Enter the length and width of your pergola (outside dimensions).
- Select post height — 8' is standard; account for buried depth separately.
- Choose rafter spacing — 16" OC is most common for 2×8 rafters.
- Optionally add purlins (the cross pieces on top of rafters for shade).
- Set rafter overhang — 12" per side is typical for a decorative look.
The Formula
Posts = 4 (standard) or 6 (for pergolas over 16' long)
Beams = 2 doubled (4 boards total, each = width + overhang)
Rafters = (Width ÷ Spacing) + 1
Rafter Length = Length + (2 × Overhang)
Purlins = (Length ÷ Purlin Spacing) + 1
Posts are 6×6 for standard pergolas. Beams are doubled 2×10s. Rafters are 2×8s. Purlins (shade slats) are typically 2×2s.