Horizontal Fence Calculator

Why a horizontal fence needs its own calculator

A vertical picket fence is counted in pickets per foot. A horizontal fence is counted in rows per section, and that changes everything downstream. Each board runs from one post to the next, so the post spacing sets the length of every piece you cut, and the stock length you buy decides how much of each board ends up on the offcut pile. Get the spacing and the stock length to agree and the waste is close to zero; get them wrong and a third of the timber you paid for goes in the skip.

The height works differently too. Boards are sold by nominal size, but a 1x6 is 5.5 inches wide, and every gap you leave adds up over twelve or more rows. On a 6 ft fence, a half-inch gap versus no gap is the difference between 13 and 14 rows — one extra board in every single bay.

Posts: closer than you are used to

Standard vertical fences put posts 8 ft apart because the rails carry the pickets. A horizontal fence has no rails: the boards are the structure. A 1x board supported only at its ends will sag over 8 ft, so 6 ft on centre is the norm. If the design calls for wider bays, add a vertical 2x4 at mid-span of each section for the boards to screw into; switch on the centre stud option and the calculator counts them and the extra screws.

Set the posts in concrete to the usual depth — a third of the post above ground is a good rule, with at least 24 inches in the ground. The post depth calculator and the concrete calculator size the holes and bags exactly; this page assumes two 50 lb bags per post.

Choosing boards

Cedar is the default for a reason: it stays flat. Horizontal boards show every cup and twist because your eye follows the long lines of the gaps. If you use pressure-treated pine to save money, buy kiln-dried-after-treatment stock or let the boards dry stacked with spacers for a couple of weeks. Wider boards mean fewer rows and less labour, but they move more with the weather; 1x6 is the usual compromise.

Face-screwing is standard. Use exterior-rated screws — the same coated or stainless deck screws you would use outdoors on a deck. The Smart Decking Calculator has a screw and hidden-fastener calculator if you want a finer count for the fastener budget.

Level is everything

Start the bottom row 2 inches off the ground so it does not wick water, set it dead level with a long level or a string line, then stack every row on spacer blocks. Check level every third row; small errors compound. On sloping ground a horizontal fence has to step down section by section — see the fence on a slope calculator for the step height and the longer downhill posts. A 2 to 4 inch gravel base under each post hole keeps the post end draining; the Smart Gravel Calculator works out how much to order.

Finishing and cost

Seal or stain within a few weeks of building, before the boards grey and check. Horizontal boards hold water on their top edges, so a penetrating oil stain lasts better than a film finish. Size the stain with the stain calculator — remember a horizontal fence has two faces and the board edges.

The default prices above are typical big-box figures for 12 ft cedar 1x6 and 4x4 posts in 2026; replace them with your local quotes. For a side-by-side with other styles, compare the total against the privacy fence calculator or the board on board calculator, and see installed cost if you are hiring it out.