⛱️Pergola Calculator
Plan a pergola's posts, beams, rafters, purlins, hardware and footing concrete.
Your pergola
You'll need
6 posts
4 beam boards · 10 rafters · 6 purlins · 12 bags of concrete
posts
6
beams
4
rafters
10
purlins
6
80 lb bags
12
🛒 Shopping list
- Posts (6×6 × 10 ft)6 posts
- Beams (2×10 × 14 ft)4 boards
- Rafters (2×8 × 12 ft)10 boards
- Purlins (2×2 × 14 ft)6 boards
- Carriage bolts (beam to post)24 bolts
- Rafter ties / hurricane clips20 ties
- Concrete for post footings (80 lb)12 bags
Footing depth and post size depend on your frost line and wind — check local code, especially for taller pergolas.
How it works
Posts per side = length ÷ max post spacing, rounded up, + 1 (two sides). Beams are doubled on each long side (4 boards). Rafters = length × 12 ÷ rafter spacing + 1. Purlins run across the rafters every 24 in. Each post gets 4 carriage bolts and 2 bags of concrete; each rafter gets 2 ties. Beams and purlins include a 1 ft overhang at each end.
Worked example
A 12 × 10 ft pergola, 8 ft tall, posts no more than 10 ft apart and rafters every 16 in: 6 posts (10 ft), 4 beam boards (14 ft), 10 rafters (12 ft), 6 purlins, 24 bolts, 20 ties and 12 bags of concrete.
Questions people ask
About 8–10 ft with 2×10 beams; longer spans need bigger beams.
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Last updated October 8, 2026. These results are friendly estimates to help you plan — always double-check before buying or making big decisions.