Fence Calculator
- Free forever
- No sign-up
- Runs in your browser
Work out how many posts, pickets or panels, rails and bags of concrete you need for a fence, in feet or metres, with an optional cost.
Add prices to estimate the cost (optional)
How it’s calculated
- Sections = fence length ÷ post spacing, rounded up. Posts = sections + 1, plus 1 for every corner and every gate.
- Pickets = (length + gap) ÷ (picket width + gap), rounded up. Gates are taken off the length first.
- Panels = (length − post width) ÷ (panel width + post width), rounded up. Posts = panels + 1.
- Rails = sections × rails per section.
- Concrete per post = (π × hole diameter² ÷ 4 − post width²) × hole depth.
Example: a 100 ft fence, 6 ft high, posts every 8 ft, 5.5 in pickets with no gap, 3 rails, and 4×4 posts (3.5 in wide) in 12 in × 24 in holes. 100 ÷ 8 = 12.5, so 13 sections and 14 posts. 1,200 in ÷ 5.5 in = 218.2, so 219 pickets (230 with 5% extra). 13 × 3 = 39 rails (41 with 5%). Each hole takes (π × 12² ÷ 4 − 3.5²) × 24 = 2,420 cubic inches, or 1.40 cu ft, so 14 posts need 19.6 cu ft: 33 bags of 80 lb premix at 0.60 cu ft each.
In metric: 30 m with posts every 2.4 m gives 13 sections and 14 posts. 14 cm boards need 3,000 ÷ 14 = 214.3, so 215 (226 with 5% extra). 10 cm posts in 30 cm × 60 cm holes take 0.036 m³ of concrete each, 0.51 m³ in all: 44 bags of 25 kg.
About Fence Calculator
Plan a wood or vinyl fence before you buy anything. Enter the length and height, choose pickets nailed to rails or ready-made panels, and the calculator counts the posts, boards or panels, rails and the bags of concrete to set the posts. Corners and gates each add a post. Type in prices if you want a rough materials cost. The formulas and a worked example in feet and in metres are under the calculator, so you can check every number.
How to use Fence Calculator
- Choose your units and the fence type: pickets on rails, or ready-made panels.
- Enter the fence length and height, the post spacing or panel width, and how many corners and gates there are.
- Check the picket width and gap, the post width and the hole size, and pick the concrete bag size you buy.
- Read the posts, pickets or panels, rails and bags of concrete. Open Add prices for an estimated materials cost.
How your data is handled
Everything is worked out in your browser as you type. Nothing you enter is sent or saved, apart from your choice of metric or imperial units and currency, which are remembered on your device.
Limits and accuracy
- It treats the fence as straight runs with even spacing. Slopes, steps, curves and fixed post positions can change the count, so mark the posts on the ground before you buy.
- Gates are taken off the length and add one post each. A gate that splits the fence into lengths that don't divide evenly by the spacing can need one more post.
- Concrete is worked out for the full hole depth around a square post. Gravel at the bottom of each hole means a little less concrete.
Questions and answers
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. A 100 ft fence with posts every 8 ft has 13 sections and 14 posts. Add one post for every corner and every gate.
How far apart should fence posts be?
Many wood fences have posts 6 to 8 ft (about 1.8 to 2.4 m) apart, often set by the length of the rails or panels. The right spacing depends on the fence, the wind and the ground, so follow the panel maker's instructions and any local rules.
How deep should fence post holes be?
HGTV's guide says one-third to one-half of the post's height above ground, so 2 to 3 ft for a 6 ft fence, and about three times as wide as the post: a 12 in hole for a 4×4. In cold places the holes may need to go below the frost line, so ask your local building office.
How many pickets do I need for my fence?
Divide the length by the picket width plus the gap, and round up. 100 ft is 1,200 in, so 5.5 in pickets with no gap need 1,200 ÷ 5.5 = 218.2, or 219 pickets. With a 0.5 in gap it's (1,200 + 0.5) ÷ 6 = 200.1, or 201 pickets.
How much concrete do I need per fence post?
Work out the hole and take away the post. A 12 in wide, 24 in deep hole around a 4×4 post (3.5 in) holds about 1.4 cu ft of concrete. Quikrete's 80 lb bag makes about 0.60 cu ft, so that's 2 to 3 bags per post.
Should I buy extra material?
A little, yes. Boards split, some are warped, and cuts waste wood. The calculator adds 5% to the pickets, panels and rails by default. Posts and concrete are counted exactly, so add a spare post if you like.
Can I work it out in metres?
Yes. Choose Metric under Units: lengths are in metres, picket and post sizes in centimetres, and the numbers you already typed are converted for you.