Size by function
Post spacing & beam guidance
Rules of thumb from dealer/manufacturer practice (Pergola Depot post layouts; beam span thumb rules). Not structural engineering — verify with the AWC span calculator or local code.
Rafter spacing & shade coverage
Material estimator
Cost estimator
Ballpark material prices — edit in the calculator logic with your local quotes. Pro install ≈ 2x materials.
Patio coverage planner
Standard pergola sizes
Dealer standard kit dimensions (Pergola Depot): overall tip-to-tip, rafter/beam lumber lengths, and post-to-post spacing. Outside = to outer post faces.
| Kit | Type | Rafter | Beam | Inside post-to-post | Outside post-to-post | Metric |
|---|
Method & sources
- Post layouts follow Pergola Depot kit dimensions: freestanding posts sit ~4 ft inside the overall footprint; attached kits gain ~2 ft on the ledger side.
- Beam spans are industry rules of thumb (doubled 2x8 to 12 ft, doubled 2x10 to 16 ft, doubled 2x12 to 20 ft) — not structural engineering. Verify with the AWC span calculator or local code.
- Rafter spacing: 12 in on-center typical, 16 in for spans over ~14 ft (OZCO Building Products).
- Shade % is a high-noon geometric model (width ÷ spacing); real shade varies with sun angle, rafter depth, and latitude.
- Costs are editable ballparks, not quotes. A 12x14 ft pergola typically runs $800-$3,000 in materials (pine vs cedar).
Pergola sizing FAQs
What size pergola do I need for 6 people?
Plan about 20 sq ft per person for dining, so 6 people need roughly 120 sq ft - a 10x12 ft pergola kit. For lounge seating allow about 30 sq ft per person (6 people = 180 sq ft, a 12x16 ft kit).
How far apart should pergola posts be?
On standard freestanding kits, posts sit about 4 ft inside the overall footprint: a 12x16 ft kit has 8x12 ft post-to-post spacing (Pergola Depot dimensions). As a rule of thumb, keep beam spans at 12 ft or less on doubled 2x8 beams; add intermediate posts for longer spans.
What size beam should I use for a pergola?
Common rules of thumb: doubled 2x8 beams for spans up to 12 ft, doubled 2x10 up to 16 ft, doubled 2x12 up to 20 ft. Use 6x6 posts when post spacing exceeds 6 ft. These are planning rules of thumb, not structural engineering - verify with the AWC span calculator or your local building code.
How far apart should pergola rafters be?
12 inches on-center is typical; use 16 inches on-center for spans over about 14 ft so the beams are not overloaded (OZCO Building Products). A 20 ft beam at 16 in on-center needs 16 rafters in an edge-to-edge layout (15 in OZCO's 1-ft inset layout).
How much shade does a pergola provide?
At high noon, shade is roughly the rafter width divided by the spacing: 2-inch rafters at 16 in on-center give about 12.5% shade. Adding 2-inch purlins at 8 in on-center on top raises combined shade to about 34%. Real shade varies with sun angle, rafter depth, and latitude.
How much does it cost to build a pergola?
Materials for a 12x14 ft pergola typically run $800-$3,000 (pressure-treated pine vs cedar). Use the cost mode above: it totals lumber linear feet plus concrete and hardware, with editable prices for PT lumber, cedar, and aluminum kits, and a DIY vs pro-install toggle.
Do I need a permit to build a pergola?
Often yes for attached or permanent structures, commonly above about 200 sq ft; some areas exempt small open-roof pergolas. Rules vary widely, so check your local building department and HOA before buying materials.
Attached vs freestanding pergola - which is better?
Attached pergolas bolt a ledger to the house, gaining about 2 ft of inside space (a 12x16 ft attached kit gives 10x12 ft inside vs 8x12 ft freestanding, per Pergola Depot). Freestanding pergolas go anywhere in the yard but need 4-6 posts with proper footings.
Can I build a pergola on a deck?
Yes, if the deck framing can carry the concentrated post loads - otherwise set independent footings beside or through the deck. Size the deck itself with our deck size calculator; a pergola is the overhead structure, while a shed is a fully enclosed building (see shed size calculator).