How to Calculate Fence Materials on a Slope
On sloped ground, measure along the ground rather than in a straight horizontal line, and decide early between a stepped fence (level sections that step down the hill) and a racked fence (sections that follow the slope). The choice changes which posts you buy and how many pickets you cut.
Quick Calculator
Posts
16
Concrete
32
Pickets
320
Rails
39
Est. Cost
$1,500–$2,500
Detailed Answer
Measure along the ground. On a gentle slope, ground length is only slightly longer than horizontal distance. 100 ft horizontal with a 10 ft drop is about 100.5 ft along the slope, so your post count barely changes.
Stepped fence: each section stays level and steps down. Works with pre-built panels. Leaves triangular gaps under the low side of each section. Posts at each step need extra length to cover the drop.
Racked fence: rails follow the slope and pickets stay vertical. No gaps at the bottom, but pickets and rails must be cut at an angle. Best for stick-built wood and for rackable aluminum panels.
Material adjustments: buy posts 1–2 feet longer on the downhill side for stepped fences, and add about 10% extra pickets for angled cuts and waste.
Recommended Materials
Pressure-Treated Fence Post 4×4×8
Ground-contact rated, ideal for all fence types.
$12 – $18
Cedar Dog-Ear Picket 1×6×6
Naturally rot-resistant, smooth on one side.
$3 – $6
Quikrete 60 lb Fast-Setting Concrete
Sets in 20-40 minutes. No mixing required.
$5 – $7
Post Hole Digger – Fiberglass Handle
Heavy-duty clamshell digger for clean holes.
$35 – $55
Simpson Strong-Tie Fence Bracket
Galvanized L-bracket for rail-to-post connections.
$4 – $8
Decorative Post Cap 4×4
Copper-top cap, fits standard 4×4 posts.
$5 – $12