Sawhorse Calc

Fence calculator

Enter the fence length, height and post spacing. You get the posts, rails, pickets and bags of concrete, with gates taken out and the hole depth worked out for you.

Fence, posts and pickets

Starting figures are typical. Type the ones on your product or quote if you have them.

Cost (optional)

14 posts

Sections
13
Rails
39
Pickets
230
Bags of concrete
22
Hole depth
2.0 ft
Post length, at least
8.0 ft

How to work it out

  1. Measure the full length of the fence line, gates included. For a fence with several sides, add the sides together.
  2. Choose the post spacing. Wood fences usually have posts 6 to 8 ft apart; check your panel or material width.
  3. Pick the rails: two per section for fences up to about 4 ft, three for 5 to 6 ft fences.
  4. Set the gap between pickets: 0 for a privacy fence, or the space you want for a picket fence. Add any gates and their width.

Rules of thumb

ItemTypical
Post spacing, wood6 to 8 ft
Post hole widthAbout 3 times the post, 10 to 12 in for a 4x4
Post hole depthA third of the height above ground, at least 2 ft
80 lb bag of concreteAbout 0.6 cu ft
50 lb bag of concreteAbout 0.375 cu ft

These are common starting points. Your site, climate and supplier may call for something different.

A worked example

100 ft of 6 ft privacy fence with posts 8 ft apart has 13 sections and 14 posts. With 3 rails per section that is 39 rails, and 5.5 in pickets touching edge to edge need 1,200 รท 5.5 = 219, or 230 with 5% extra. Holes 10 in wide and 2 ft deep take about 22 bags of 80 lb concrete.

Corners, frost and rules

Each corner where the fence changes direction usually needs its own post, so add one per corner. In cold areas, posts often need to go below the frost line, which can be deeper than 2 ft; local codes, HOA rules and property lines also matter, and call 811 before you dig to have buried lines marked.

Common questions

How many fence posts do I need?

Divide the fence length by the post spacing and round up to get the sections, then add one post. Add one more for each gate and each corner. 100 ft at 8 ft spacing needs 14 posts.

How many pickets do I need?

Divide the fence length in inches by the picket width plus the gap. A 100 ft privacy fence of 5.5 in pickets needs about 219, so buy around 230.

How many bags of concrete per fence post?

For a 10 in hole 2 ft deep around a 4x4 post, about 0.92 cu ft, which is 1 to 2 bags of 80 lb concrete. Bigger or deeper holes take more.

How deep should fence posts be?

A common rule is a third of the post's height above ground, and at least 2 ft. A 6 ft fence needs 2 ft in the ground, so an 8 ft post. In cold climates go below the frost line.

How many rails does a fence need?

Usually two rails per section for fences up to about 4 ft and three for 5 to 6 ft fences, so the pickets do not bow.

Doing this job for a customer? Turn your numbers into a free written estimate on QuoteToPaid.

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