Free Pergola Calculator
This free pergola calculator turns three numbers — length, width, and height — into a complete pergola plan sheet: a lumber shopping list in stock lengths, a full cut list, concrete footing counts, a hardware schedule down to the last bracket, and a cost estimate you can tune with your local prices. Imperial or metric, posts in the ground or mounted to concrete, classic build or the bracket system I used for my 2-hour pergola build. No account, and the tool is free to use without giving an email.
Design your pergola — any size, posts in the ground or mounted to concrete, a traditional slatted top or a modern open top — and get the full shopping list, a custom cut list, and a realistic cost estimate. Imperial or metric. No sign-up needed to see your results.
Your pergola, to scale
Shopping list — for 10' × 10' × 8'
| Qty | Item | Get it |
|---|
Your custom cut list
| Part | Qty | Length | Material |
|---|
Beams sandwich the posts in pairs with two ½″ carriage bolts per post. Rafters sit on the beams with a hurricane tie at each crossing; slats screw down to the rafters. On pergolas longer than 8′, the 2×2 slats are spliced — every joint lands on a rafter, and you stagger the joints between neighboring slats so no seam lines up. Cut rafter tails to your favorite profile before hanging.
📩 Email me my pergola plan sheet
Get this cut list, shopping list, and cost estimate for 10' × 10' × 8' sent to your inbox — free.
The hardware that holds it together
Note: This is general planning guidance using rule-of-thumb spans. A pergola is a structure — verify spans, footing depth, wind/snow loads, and setbacks against your local building code before you build. Lumber figures use actual (not nominal) dimensions; confirm quantities before purchasing.
A free tool from Rogue Engineer. Be safe and happy building.
Two ways to build a pergola — the calculator prices both
The bracket build is the one that surprises people: posts run all the way to the top, a steel bracket slips over each post, and beam segments — cut from the same stock as your posts — drop in between on all four sides. No angle cuts, no drilling through posts, no second pair of hands holding a beam overhead. Simpson’s Sage system is the premium version and Amazon carries budget equivalents; the calculator swaps the hardware schedule and prices when you pick.
The traditional build sandwiches each post between doubled 2×10 beams bolted through with carriage bolts, rafters riding on top with a tie at every crossing, and 2×2 slats over that. It’s more cutting and more ladder time, but it’s the classic profile — and on longer spans the calculator adds knee braces and warns you when a span outgrows the post size, so the lumber list you get is one that actually stands up straight.
Footings: less concrete than you think
For posts in the ground, the calculator digs to your frost depth and sets each post on a 4″ concrete footing pad — a “cookie” at the bottom of the hole — then backfills around the post with gravel or dirt, tamped in lifts. It’s a method that drains better than a full concrete collar and uses a fraction of the bags: one 80-lb bag typically pads two or three posts. Building on an existing slab or footings instead? Switch to mounted mode and the concrete disappears from the list, replaced by standoff post bases that keep the post ends dry.
How to use the pergola calculator
1. Size it. Length runs with the beams, width with the rafters, both including overhangs; height is grade to the underside of the beams. Presets cover the common sizes if you want a starting point.
2. Pick your structure. Post size, footing type, top style, and rafter/slat spacing — the shade-coverage percentage updates live, so you can see what 12″ slat spacing buys you over 16″ before you pay for the extra lumber.
3. Make the estimate yours. Every unit price — lumber per linear foot, concrete per bag, post bases each — is editable. Plug in your local numbers and the low–high range becomes a real budget.
4. Email yourself the plan sheet. The exact cut list, shopping list, and cost for your pergola, in your inbox — free, and sized to your yard instead of a catalog’s.
What size pergola should you build?
The calculator covers 6 to 20 feet long, 6 to 16 wide, and 6 to 10 tall, with one-click presets for the two sizes people actually build most: 8×8 for a corner or a grill zone, and 10×10 — the size of my own build, big enough for a dining table without dominating the yard. Length runs with the beams and width with the rafters, so a 12×16 and a 16×12 are different structures with different lumber lists.
Go bigger and the calculator quietly restructures things for you: when the end beams span past the clear-span guideline for your post size it calls for a mid post on each end (or a step up to 6×6 posts), long 2×2 slat runs get spliced with every joint landing on a rafter, and 2×4 slats spanning more than 8 feet trigger a sag warning before they trigger actual sag. That’s the difference between a lumber list and a plan.
Pergola calculator FAQ
What does the pergola calculator give me?
A complete plan sheet for your exact size: every post, beam, rafter, and slat as a cut list, a lumber shopping list in stock lengths, the concrete and hardware counts, and a cost estimate. Enter your dimensions and it updates instantly — then email yourself the whole sheet, free.
Which build method should I pick — brackets or traditional?
The bracket build (Simpson Sage-style or budget Amazon versions) is the fast one: posts run to the top, a bracket slips over each post, and the beam segments drop in — no angle cuts and no drilling through posts. It’s how I built a 10×10 pergola in about two hours, solo. The traditional build sandwiches the posts between doubled beams with carriage bolts and takes longer, but it’s the classic look and handles bigger tops. The calculator prices both.
How much concrete do pergola posts need?
Less than most people pour. Instead of filling each hole, the calculator uses a 4-inch concrete footing pad at the bottom — set the post on it and backfill with gravel or dirt, tamped in lifts. One 80-lb bag typically covers the pads for two or three posts. Mounting to an existing slab instead? It swaps the concrete for standoff post bases.
Is the cost estimate accurate for my area?
It’s built from prices you control. The calculator ships with mid-2026 national numbers per linear foot of lumber, per concrete bag, and per post base — and every one is editable, so you can plug in your local quotes and get a real number, shown as a low–high range to cover the sales-tax-and-oops factor.
Does the calculator work in metric?
Yes — flip the m / cm toggle and every input, cut length, and the plan-sheet email switch to metric, with lumber sizes shown in millimeter equivalents.
What spacing should I use for rafters and slats?
The calculator defaults to rafters 16 inches on center and top slats 12 inches, which reads as a classic pergola top. Tighten the slats to 8 inches for more shade or spread everything to 24 for a lighter look — the shade-coverage percentage updates so you can see the trade before you buy lumber.
From plan sheet to standing pergola
When you’re ready to build, the full pergola build guide walks my 10×10 bracket build step by step — layout, squaring the top frame on the ground, anchoring the bases, standing the posts, and the two-hour part everyone doubts until they watch it happen. It covers the traditional method too, plus what we added around the finished space.
