Calculate fence post count, spacing, and concrete per post. Enter fence length and desired spacing for accurate post and footing estimates.
Fence post spacing is the foundation of any fence project. Get it right, and your fence stands straight and strong for decades. Get it wrong, and you'll deal with sagging panels, leaning posts, and costly repairs.
This calculator determines the number of posts, adjusts spacing for equal bays, and estimates the concrete needed for each post hole. Standard fence post spacing is 6–8 feet on center, depending on fence height, wind exposure, and design. Each post typically needs a hole 10‒12 inches in diameter and 24‒36 inches deep, filled with quick-setting concrete.
Whether you're planning a new fence or replacing posts on an existing one, this tool ensures even spacing and accurate material estimates.
Tracking this metric throughout the project lifecycle helps project managers identify potential issues early and maintain quality standards from foundation to final inspection. Integrating this calculation into the estimating workflow reduces reliance on rules of thumb and improves the accuracy of material takeoffs and budget projections for every job.
Even post spacing is essential for a professional-looking fence. Simply dividing the length by the spacing leaves odd partial bays. This calculator adjusts for equal bay widths so every section looks uniform. Regular use of this calculation supports compliance with building codes and inspection requirements, helping projects proceed smoothly through the permitting and approval process.
Posts = (Length ÷ Spacing) + 1 (rounded up) Adjusted Spacing = Length ÷ (Posts − 1) Concrete per Post = π × (Hole Radius)² × Depth
Result: 14 posts / ~21 bags concrete
100 ft ÷ 8 = 12.5, round to 13 bays + 1 = 14 posts. Adjusted spacing: 100 ÷ 13 = 7.69 ft (equal bays). Each hole: π × 5² × 24 = 1,885 in³ = 0.04 yd³ ≈ 1.5 bags, total: 21 bags.
If you just set posts at exact 8-ft intervals on a 100-ft fence, the last bay will be 4 ft — half the width of every other section. This looks sloppy and wastes a panel. Adjusting all bays to an equal width (like 7.69 ft) creates a professional, balanced appearance.
Dig holes 3× the post width and at least 24 inches deep. Taper the hole wider at the bottom for a bell shape that resists frost heaving. Place 3 inches of gravel at the bottom for drainage before setting the post.
For dry-pack (pour dry mix, add water): fill around the post in layers, wetting each 6-inch lift. For premixed: mix concrete in a wheelbarrow or mixing tub and pour around the post. Crown the concrete above grade to shed water away from the post.
Gate openings interrupt the regular spacing. Set gate posts at the desired opening width, then space the remaining line posts equally on each side. Corner posts count as two endpoints — calculate each fence leg separately.
The standard is 8 feet on center for most residential fences using 4×4 posts and 2×4 rails. Wind-prone areas and tall fences (over 6 ft) should use 6-foot spacing for added strength.
Posts should be buried at least 1/3 of their total length, with a minimum of 24 inches. In cold climates, set posts below the frost line (36‒48 inches in northern states). Deeper is always better for stability.
A standard 10-inch diameter hole that's 24 inches deep needs about 1–2 bags (50–80 lb each) of premixed concrete. A 12-inch hole at 30 inches deep needs 2–3 bags. Check the bag coverage chart for your brand.
Yes, in firm clay soil, tamped earth or gravel can work for short-lived fences. However, concrete provides dramatically better strength and longevity. It's strongly recommended for any permanent fence installation.
After determining the number of posts, divide the total length by (posts − 1) to get the adjusted even spacing. This may be slightly different from your target spacing, but it ensures all bays are equal.
Use 4×4 posts for standard fences up to 6 feet. Use 6×6 posts for gate posts, corner posts, fences over 6 feet, and high-wind areas. Gate posts take the most stress and should always be 6×6.