Pergola Material Calculator
Posts, beams, rafters and slats for a pergola build.
Enter your values
ⓘ Live results
Results
- Posts
- 4 x 10 ft (6x6 recommended)
- Beams
- 4 x 12 ft
- Rafters
- 10 x 10 ft
- Purlins
- 11 x 12 ft
- Total lumber
- 320 linear ft
- Lumber cost
- $1,120.00
Working
- 1rafters 10 + purlins 11 -> 320 linear ft total
Quick answer
A pergola needs 4+ posts, two beams per side, rafters at your chosen spacing across the span, and optional top purlins.
rafters = width / spacing + 1
How to use the Pergola Material Calculator
- 1Set the pergola footprint and choose rafter spacing - 16 to 24 inches is typical.
- 2Add purlins on top if you want more shade.
- 3Price the total linear feet at your local lumber rate.
Worked example
Using the values the calculator loads with:
Inputs
- Pergola length12 ft
- Pergola width10 ft
- Rafter spacing16 in
- Purlin spacing12 in
- Cost per linear foot3.50 $
Results
- Posts4 x 10 ft (6x6 recommended)
- Beams4 x 12 ft
- Rafters10 x 10 ft
- Purlins11 x 12 ft
- Total lumber320 linear ft
- Lumber cost$1,120.00
- rafters 10 + purlins 11 -> 320 linear ft total
Frequently asked questions
How much shade does a pergola give?
Rafters alone give roughly 30 to 40% shade. Adding purlins on top pushes it toward 60 to 70% at midday.
What size posts for a pergola?
6x6 for anything over 8 ft tall or 10 ft span. 4x4 posts look spindly and flex in wind.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.