Fence Calculator

Fence materials in 30 seconds

For a standard wood fence, plan one post every 8 feet, plus an extra post at every corner and on each side of every gate. Use two rails for fences under 5 ft tall, three rails for 6 ft and up. Pickets are calculated by total linear feet (in inches) divided by picket-plus-gap width. One bag of fast-set concrete per standard post, two for corner and gate posts. The calculator above does all five at once and adds 10% waste.

How to estimate fence materials

Every fence job follows the same five-step takeoff. Get the linear footage, pick post spacing, count corners and gates, choose picket style, and figure rails. Miss any one of those and you'll end up short or way over-ordered. The calculator above runs the math automatically, but here's how it works under the hood so you can sanity-check the numbers.

How far apart should fence posts be?

Standard post spacing for residential wood fence is 8 feet on center. Drop to 6 feet for heavy privacy panels, sites with high wind, or sandy/loose soil where posts need extra grip. Chain link runs 10 feet on center. Tighter spacing costs more in posts and concrete but builds a noticeably stronger fence — privacy panels stop sagging, gates don't pull the fence out of plumb, and the whole assembly takes wind better. Spacing math: divide your total fence length by the spacing, round up, and add 1 for the end post.

How deep should fence posts be?

The classic rule is one-third of the post above ground goes below ground. For a 6-foot fence, that means digging 2-foot holes and using 8-foot posts. Frost regions need to go deeper — below the frost line, which is typically 36 inches in the Mid-Atlantic, 42–48 inches in the Upper Midwest, and 60 inches in interior Alaska. Posts set above the frost line will heave every winter and your fence will lean within a few seasons.

Add 6 inches of gravel below the post for drainage. In frost regions, override the table and dig to local frost depth.

How much concrete per fence post?

For a standard 4x4 post in a 10-inch diameter, 24-inch deep hole, one 50-lb bag of fast-set concrete is the right amount. For a 6x6 post, gate post, or corner post in a 12-inch diameter, 30-inch deep hole, plan on two bags. Fast-set saves time — you can set the post, plumb it, brace it, and move on without the next-day return trip. Standard concrete needs 24 hours before you can hang anything off the post. For large jobs (50+ posts) calculate by volume: a 10-inch round, 24-inch deep hole holds about 0.45 cubic feet, which is roughly one 50-lb bag.

Fence picket spacing and quantity

How you space pickets depends on fence style.

• Privacy fence — pickets butt tight against each other. If the wood is wet (as pressure-treated lumber usually is), leave a 1/8 inch gap so it doesn't buckle when it dries and shrinks.
• Shadow box / board on board — alternating pickets on opposite sides of the rail, overlapping by about an inch. Looks the same from both sides.
• Picket fence — 2.5 to 3 inches of gap between pickets. The gap should match the picket width for a balanced look (e.g., 3.5-inch picket with a 3-inch gap).
• Spaced board — 1 to 2 inches of gap. Gives privacy without total enclosure, common in modern designs.

Quantity formula: total fence length in inches ÷ (picket width + gap) = number of pickets. A 100-ft fence with 5.5-inch pickets butted tight needs 100 × 12 ÷ 5.5 = 218 pickets.

What size lumber should I use for rails?

Rails take all the lateral load from wind and impacts and transfer it to the posts. Underspec the rails and the fence sags or pulls apart at the joints. Use 2x4 rails for fences up to 8 feet between posts. For longer spans or heavy 6-foot privacy panels, step up to 2x6 to prevent mid-span deflection. Number of rails depends on fence height: two rails (top and bottom) for fences under 5 feet; three rails (top, middle, bottom) for 6 feet and up. The middle rail is what keeps tall pickets from cupping or twisting over time.

Ordering extra materials

Always pad your order. Boards split when you nail them, knots blow out under fasteners, miters waste material, and rough lumber sometimes shows up warped past saving. Standard waste factors:

• Pickets: order 10% extra. 15% if you're cutting decorative tops.
• Rails: order 5% extra unless your spans are odd lengths that force a lot of cuts.
• Posts: order exact for straight runs. Add one or two extra for jobs with corners or angles.
• Concrete: order 10% extra. Rookie holes always come out a bit oversized.
• Fasteners: never run short — buy a full extra box for any job over 100 ft.

Returning unused lumber costs you 15 minutes. Driving back to the lumber yard mid-job costs you a half-day of crew labor. Always pad up.

Permits and property lines

Most cities require a permit for fences over 6 feet. Some require one for any fence at all. Front-yard fences usually have a height cap of 4 feet under most municipal codes; backyards can go to 6 feet without variance, occasionally 8 with one. Always pull the permit before you dig — getting caught means tearing the fence down. Just as critical: get a property line survey or pull the official plat. Building a fence even 6 inches over the line gives you two bad outcomes: an angry neighbor or a forced removal at your expense.