Pergola Footing Calculator
Every pergola post needs its own concrete footing, and the number depends on your layout size and how far apart you space the posts. Enter your pergola dimensions and post spacing, and this calculator works out footing count and total cost.
Covers curves, corners and offcuts. 5–15% is normal.
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For a rectangular pergola, add up the perimeter (twice the length plus twice the width), then divide by your chosen post spacing and round up to get the footing count. Wider post spacing means fewer, deeper footings supporting longer beam spans; tighter spacing means more, often shallower footings. Multiply the footing count by the price per footing (which includes the concrete, form, and labor to dig and pour it) to get total cost.
Pergola Footing Depth by Frost Line
Footing depth should go below your local frost line to prevent frost heave from cracking or shifting posts over winter. Check with your local building department for the exact frost depth in your area.
| Region / Frost Line | Minimum Footing Depth | Typical Footing Diameter |
|---|---|---|
| No frost / mild climate | 12-18 in below grade | 10-12 in dia |
| Moderate frost line (24-36 in) | 24-36 in below grade | 12 in dia |
| Deep frost line (36 in+) | 36-48 in below grade | 12 in dia |
| Large pergola / heavy beams | 24-36 in, widen the footing | 12-16 in dia |
How to calculate pergola footings
- Lay out your pergola as a straight run or a rectangle, and note the length and width.
- Calculate the perimeter twice the length plus twice the width for a rectangle.
- Choose a post spacing 6-10 ft depending on beam size and how much span the structure needs to carry.
- Divide perimeter by spacing and round up to a whole footing, since posts can’t be partially placed.
- Price it out multiply footing count by the cost per footing, which covers concrete, form tube, and typical labor.
Worked example
Here’s a 16 ft x 12 ft rectangular pergola with 8 ft post spacing and no added waste.
- Layout16 ft x 12 ft rectangle
- Perimeter56 ft
- Post spacing selected8 ft
- Waste added0%
- Footings needed7 footings
- Footing size12 in dia x 24 in deep
- Footing cost (7 x $85)$595
- Total estimated cost$595
Spacing Math Doesn’t Replace Corner Posts
This calculator divides your perimeter evenly by post spacing to get a footing count, which is the right way to estimate total footings and cost. But when you actually lay out the pergola, always place a post and footing at every corner first, then fill in the remaining spacing between corners as evenly as possible. Don’t just mark off even intervals around the whole perimeter without regard for where the corners land, or you can end up with an oddly placed post right next to a corner instead of a clean corner post. Also check your beam span rating before committing to wide spacing. A 6 ft spacing needs a much smaller beam than a 10 ft spacing to avoid sag under snow or wind load.
Common mistakes
- Ignoring frost depthfootings poured above the local frost line can heave and crack over winter, shifting posts out of plumb.
- Spacing without planning cornerseven spacing math needs to be adjusted so a footing lands at every corner, not just at mathematically even intervals.
- Undersized beams for wide spacingwider post spacing means longer beam spans, which need larger lumber or engineered beams to avoid sag.
- Skipping post anchorsfootings need embedded post bases or anchors specified before the pour, not added afterward.
What this calculator assumes
Adjust your result if your project differs from these.
- Footing count is based on even post spacing around a straight run or rectangular perimeter.
- Footings are sold as a complete unit, including concrete, form tube, and typical dig/pour labor.
- A footing is always placed at each corner in practice, even though the spacing math is applied evenly.
- Depth and diameter shown are typical for the post spacing chosen, not adjusted for local frost line automatically.
- Post anchors, hardware, and the posts and beams themselves are priced separately from footings.
Common questions
How many footings does a 16×12 pergola need?
With 8 ft post spacing, a 16 ft x 12 ft pergola (56 ft perimeter) needs 7 footings.
How deep should a pergola footing be?
Deep enough to clear your local frost line, typically 24-36 in in moderate climates and up to 48 in in deep-frost regions. Check local code.
What post spacing should I use for a pergola?
6-8 ft is standard for residential pergolas with typical beam sizes. Spacing beyond 8-10 ft usually needs larger or engineered beams to avoid sag.
Does this calculator include the posts and beams?
No. It calculates concrete footing count and cost only. Posts, beams, and rafters are estimated and priced separately.
Do I need a footing at every corner?
Yes. Regardless of what the even-spacing math suggests, always place a footing at every corner of the layout, then space the remaining posts as evenly as possible between them.
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Notes
Estimate generated by materialcalculate.com. Confirm quantities with your supplier before ordering.