Fence Post Calculator – How Many Posts & Bags of Concrete

Find out how many fence posts to buy for any length of fence: enter the total length and post spacing, then add corners and gates. The calculator splits the count into line posts, end and corner posts, and gate posts, and suggests a post length.

Fence length	100 ft
Sections between posts	13
Posts	14 (12 line · 2 end/corner)
Post length	8 ft (6 ft above ground + 24 in in the ground)
Rails (3 per section, 8 ft long)	39
Pickets (5.5 in)	230 (incl. 5% extra)
Concrete for posts	12.89 cu ft (0.92 per post)

50 lb fast-setting (0.375 cu ft)	42 (3 per post)
60 lb (0.45 cu ft)	42 (3 per post)
80 lb (0.60 cu ft)	28 (2 per post)

It also works out the concrete for each hole from the hole width and depth, in 50, 60 and 80 lb bags — so you can buy posts and concrete in one trip.

Good to know

Posts = length ÷ spacing, rounded up, + 1 for a straight run. Corners are shared by the two sides that meet there.
Set the hole about one-third of the fence height deep, at least 24 in, and below your local frost line in cold areas.
Dig holes about 3 times the post width: 10–12 in for a 4×4.
Put 4–6 in of gravel at the bottom of each hole so water drains away from the post end.

6 ft wood privacy fence, straight run, no gates (1×6 pickets, 10 × 24 in holes)

Fence length	Posts (8 ft apart)	Posts (6 ft apart)	Rails (8 ft)	Pickets	80 lb concrete bags (8 ft)
50 ft	8	10	21	110	16
100 ft	14	18	39	219	28
150 ft	20	26	57	328	40
200 ft	26	35	75	437	52
300 ft	39	51	114	655	78

Add one post per gate and about 5% extra pickets. Corners are shared, so an L-shaped fence needs one fewer post than two separate runs.

How to use this calculator

Measure the total length along the post line and choose the layout: straight, L-shape or three sides.
Pick the style and height, and set the post spacing (or panel width for vinyl panels).
Add your gates. Open “Rails and post holes” to change the hole size or rails per section.
Optionally enter a price per foot of fence to estimate the cost.

Add this calculator to your website

Run a landscaping supply, garden center or DIY blog? Paste this code into your page to let visitors use the fence post calculator right there. It is free, has no ads, and resizes itself to fit.

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Frequently asked questions

How many fence posts do I need for 100 feet?

For a straight 100 ft fence you need 14 posts with 8 ft spacing, or 18 posts with 6 ft spacing. Add one post for every gate.

How deep should fence posts be?

About one-third of the height above ground, and at least 24 in. A 6 ft fence needs 24 in holes and 8 ft posts; an 8 ft fence needs about 32 in and 12 ft posts.

How many bags of concrete per fence post?

For a 10 in wide, 24 in deep hole around a 4×4: two 80 lb bags or three 50 lb bags of fast-setting mix. A 12 in wide hole of the same depth takes three 80 lb bags.

How do corners and gates change the post count?

A corner post is shared by the two sides that meet there, so an L-shaped fence needs one fewer post than two separate runs. A gate needs a post on each side, which adds one post to the run.