Fence Calculator
Calculate posts, rails, and pickets needed to build a wood privacy fence based on your fence length and post spacing.
How to use this fence calculator
- Measure the total perimeter of fencing needed in feet.
- Choose post spacing — 6 feet for heavy privacy fences, 8 feet for standard wood privacy fences.
- Add one post for each gate location (gates need posts on both sides).
- Add 10% to picket count for defects, cuts, and waste.
- Always call 811 (Dig Safe) before digging post holes to locate underground utilities.
Formula
Sections = ⌈length ÷ post spacing⌉. Posts = sections + 1. Rails = sections × 2. Pickets = ⌈length × 12 ÷ picket width⌉.
About the Fence Calculator
A well-built fence serves multiple functions simultaneously — privacy, security, property definition, wind buffering, and aesthetic framing of outdoor spaces. The investment in quality materials and proper installation determines whether a fence lasts 10 years or 40 years, making material selection and construction technique critical decisions.
The structural integrity of a fence depends primarily on post installation. The most common fence failure mode is post rot at or below the soil line, where moisture, oxygen, and soil microorganisms converge. Pressure-treated posts rated for ground contact (UC4B minimum), set in concrete below the frost line, prevent the most common failure mechanism. The concrete collar should slope away from the post at the top to direct water away from the wood-concrete interface.
Fencing project planning should begin with accurate property boundary identification. A survey stake is the authoritative marker — building to a fence line that turns out to be several inches into a neighbor's property creates legal and neighborly complications that are expensive to resolve. When uncertainty exists, pull fences slightly inside property lines. Local ordinances also specify setbacks — the minimum distance from property lines where structures including fences may be placed.
Cost of a wood privacy fence typically runs $15–$35 per linear foot installed (material and labor). DIY installation saves the labor component (typically 50–60% of total cost) but requires post hole digging equipment, concrete mixing, and comfort with level and plumb work. The critical skill for DIY fence building is post setting — perfectly plumb posts at the correct height create a fence that can be completed quickly and looks professional. Posts that are even slightly out of plumb or at varying heights require time-consuming compensation at every subsequent step.
Frequently asked questions
+How far apart should fence posts be?
Standard residential wood fence post spacing is 6–8 feet on center (measured from center of one post to center of the next). Six-foot spacing is used for heavier privacy fences, particularly in windy areas or with tall fences. Eight-foot spacing is the most common for standard 6-foot privacy fences and uses the standard lumber length of 8 feet for rails. Post spacing above 8 feet requires larger rails and more robust construction to prevent sagging. Corner and gate posts always require their own post regardless of spacing interval — never span across a corner or gate opening.
+How deep should fence posts be set?
The general rule is to set posts to a depth of one-third to one-half of the above-ground post height. For a 6-foot fence using 8-foot posts: bury 2–2.5 feet in the ground, leaving 5.5–6 feet above grade. In frost-prone climates (freeze-thaw cycles can heave shallow posts), set posts below the local frost depth, which ranges from 12 inches in the Southeast to 60+ inches in northern Minnesota. Confirm local frost depth with your county extension office or building department. Use concrete around posts for maximum stability — a 60 lb bag of fast-setting concrete per post hole provides excellent holding power.
+What wood is best for fence posts and pickets?
For ground-contact fence posts, pressure-treated lumber rated for ground contact (labeled UC4B or UC4C) is essential — untreated wood rots within a few years in soil contact. Common pressure-treated species include Southern yellow pine and western red cedar. For pickets and rails, pressure-treated lumber provides the longest service life. Cedar and redwood are popular alternatives that resist decay naturally and accept stain beautifully, though they cost more than pressure-treated pine. Douglas fir is sometimes used for rails but must be finished and maintained. Composite fence boards (plastic/wood fiber) offer maintenance-free performance but at higher upfront cost.
+Do I need a permit to build a fence?
Most municipalities require a permit for fences above a certain height — commonly 6 feet for rear yards and 4 feet for front yards, though this varies significantly. Permits typically involve reviewing property surveys, setback requirements (how far the fence must be from property lines), and HOA covenants in deed-restricted communities. Even when permits are not required, you must still locate your exact property lines before installing — a fence even 6 inches over the line can require expensive removal. Your local building department can tell you the requirements; 811 (Dig Safe) is a free service that marks underground utilities before you dig.