Fence Calculator – Estimate Posts, Pickets, Rails and Concrete
A fence calculator turns a sketch of your yard into a shopping list. Enter each straight run of fence, the turns between them and the gates, pick a style, and this tool counts the fence posts by type, the rails, the pickets or boards (or panels, or chain-link fabric and fittings), the gate hardware, and the concrete bags and gravel for the post holes. It also draws a plan of the layout and one section of the fence to scale, including the part of the post that sits underground.
How Fence Posts Are Counted
Gates split each run into fence segments. For every segment the calculator works out sections = ⌈length ÷ post spacing⌉ and posts = sections + 1. Where two runs meet, they share one post, so each joint is subtracted once. The posts on either side of a gate are not shared, because the gate spans between them. A 50 ft, 80 ft and 50 ft U-shaped fence at 8 ft spacing with one 4 ft gate needs 24 sections and 26 posts: 2 end posts, 2 corner posts, 2 gate posts and 20 line posts.
Post types matter when you order. Corner, end and gate posts take more load and are often a size up. In chain link they are the heavier terminal posts. Split-rail posts come pre-drilled, so the list separates through-mortised line posts, corner posts and posts mortised on one side only.
Pickets, Boards and Rails
Pickets are counted per segment and then added up, because rounding the total would undercount at every gate and corner. A solid privacy fence uses ⌈L ÷ board width⌉. A spaced picket fence uses ⌈(L + gap) ÷ (width + gap)⌉, and the even-spacing helper tells you the exact gap that repeats cleanly in each section. Board-on-board (shadowbox) fences need more wood because the two layers overlap: ⌈L ÷ (width − overlap)⌉ + 1.
Rails run post to post, and a rail joint has to land on a post. That is why the rail stock must be at least as long as the post spacing. An 8 ft on-centre spacing is popular because one 8 ft 2×4 covers exactly one section. Most 6 ft fences use 3 rails per section; 4 ft fences need 2.
How Deep to Set Posts and How Much Concrete
A common rule is to bury one third of the above-ground height, with at least 24 in (600 mm), plus about 6 in of gravel under the post for drainage. Holes are usually about three times the post width, rounded to a common auger size (10 in for a 4×4, 16 in for a 6×6). The concrete fills the ring around the post: (π × (D ÷ 2)² − post area) × embedment. For a 4×4 post in a 10 in hole 24 in deep, that is about 0.92 ft³ per post, or roughly 1.5 bags of 80 lb concrete.
Split-rail fences are often set in gravel and tamped soil instead of concrete, which drains better and makes posts easier to replace. Choose that setting and the whole hole is filled with gravel instead.
Chain Link and Pre-Built Panels
For chain-link fence the calculator counts fabric rolls, top-rail sticks (allowing for the swaged-end overlap), tension bars, tension bands, brace bands, rail end cups, carriage bolts, caps and fence ties. Each terminal post gets fittings for every side that has fabric attached. For vinyl, wood or aluminium panels the post spacing is locked to the panel width, and any segment that doesn't divide evenly gets a cut panel, listed with its cut length.
Planning Tips
- Measure along the actual fence line and mark gate positions from a fixed corner. Moving a gate so it shares a corner post saves a post and avoids a tiny, weak segment.
- On sloped ground, plan for stepping (level sections that drop at each post) or racking (panels that follow the grade). Both change post heights and can need longer posts on the downhill side. This estimate assumes level ground.
- Check your local rules before you buy. Fences over about 6 ft in back yards or 3–4 ft in front yards often need a permit or HOA approval.