Horizontal Fence Calculator

How the horizontal fence calculator works

A horizontal fence has boards running along the fence, fixed to the posts, stacked from the ground up with a small gap between them. So the first number is rows: how many boards stack to the fence height.

Rows = fence height ÷ (board width + gap), rounded up

Each row then needs enough board to span every section. The calculator assumes 8 ft boards and counts one per row per section, or more if a section is longer than a board:

Boards per section = rows × boards to span the section

Posts go at every corner, end and gate, and each straight stretch is divided into equal sections no longer than your post spacing. Boards and screws get 10% extra for waste, the allowance Inch Calculator recommends. Screws are two at each board end.

A worked example

The calculator opens on 150 ft of 6 ft horizontal fence with two corners and one 4 ft walk gate, using 1x6 boards with a 1/4 in gap and posts no more than 6 ft apart. The gate splits one of the three 50 ft sides into two 23 ft stretches, leaving 146 ft of fence.

• Rows: a 1x6 is 5 1/2 in wide, so each row takes 5.75 in. The bottom board sits 1/2 in off the ground, leaving 71.5 in: 71.5 ÷ 5.75 = 12.4, so 13 rows.
• Sections: each 23 ft stretch becomes 4 sections of 5.75 ft, and each 50 ft side 9 sections of about 5.56 ft. That is 26 sections on 28 posts.
• Boards: every section is shorter than 8 ft, so one board per row: 13 per section. 26 × 13 = 338 boards, plus 10% gives 372 boards.
• Screws: 1,488, two at each end of every board, with waste.
• Concrete: 116 bags of 50 lb fast-setting for 42 in holes.

13 rows of 5 1/2 in boards with 1/4 in gaps stack to 74 1/2 in, 3 in more than the 71 1/2 in above the ground gap. Either rip the top board to fit, or use 12 rows and open the gap to 1/2 in so the boards land exactly on 6 ft. The panel beside the material list works out both for your numbers.

Why posts go no more than 6 ft apart

Horizontal boards span from post to post with nothing behind them, so the post spacing is the board's unsupported span. The FenceRail.com installation guide for horizontal wood fences uses 3 to 6 ft post spacing. If the distance between posts is more than 6 ft, it adds a 2x4 along the center of the section. The calculator defaults to 6 ft and warns if you go wider.

The same guide leaves a 1/4 in gap between boards and at least 1/2 in between the bottom board and the ground. The calculator keeps that 1/2 in clear and counts rows over the rest of the height.

How many rows of boards?

With the 1/4 in gap:

Board widths are actual sizes: ProWood lists a 1x4 at 3 1/2 in and a 1x6 at 5 1/2 in. Narrow boards need more rows and more screws. At 6 ft, 1x4 boards need 20 rows against 13 for 1x6.

Why the board count looks high

With posts 6 ft apart and 8 ft boards, about 2 ft of every board is offcut in the example. The calculator counts it that way because it is the safe way to buy. You can cut the count in two ways:

• Buy boards to length. If your yard sells 6 ft or 12 ft boards, a 12 ft board covers two 6 ft sections with one joint on a post.
• Plan joints across posts. Longer boards that span two sections cut waste, as long as each joint lands on a post.

For comparison, one straight 100 ft run at the default settings needs 18 posts and 244 boards. At 8 ft post spacing it would need only 14 posts and 186 boards, because every 8 ft board is used in full. That is outside the 6 ft the guide allows, so it needs the center support in every section.

What people ask next

• What post spacing suits my board? The fence post spacing calculator splits a run into equal sections for any maximum.
• How much stain? Horizontal fences show a lot of board face. The fence stain calculator turns your length and height into gallons.
• Other wood styles: the wood fence calculator compares horizontal with privacy, picket, board on board and shadow box per 100 ft.
• To mix fence types or draw the whole line on a map, start from the fence calculator.