How to use the fence calculator
- Enter each run. A run is one straight line of fence from end to end or corner to corner. Add the number of gates in that run.
- Set the gate width and the number of corners shared by two runs. Two runs that meet at a corner use one post there, not two.
- Pick the height, post spacing and style: privacy (pickets touching), spaced pickets with a gap, or board on board.
- Pick the picket and post size. Sizes are shown as sold (1x6, 4x4) with their actual width, which is what the count uses.
- Leave rails, post depth and hole width blank to use the defaults shown, or type your own.
The result lists posts, rails, pickets and bags of concrete. Open Your prices to add your own price for each item and get a cost total. Choose Meters to work in meters and millimeters.
How many fence posts do I need?
For each run: sections = (run length minus gates) / post spacing, rounded up. Posts = sections + 1, plus 1 for each gate in the run. Then take off one post for each corner shared by two runs. Rails = sections x rails per section. This assumes each gate sits at the end of a run; if a gate splits a run into two parts, add one more post.
Here is a U-shaped back yard fence, 6 ft high, with posts 8 ft apart, a 4 ft gate in the last run and two corners. Press Try an example to see it in the calculator.
| Run | Fence | Sections | Posts | Pickets |
|---|---|---|---|---|
| 50 ft | 50 ft | 50 / 8 = 6.25, so 7 | 8 | 110 |
| 100 ft | 100 ft | 100 / 8 = 12.5, so 13 | 14 | 219 |
| 50 ft, 1 gate | 46 ft | 46 / 8 = 5.75, so 6 | 6 + 1 + 1 = 8 | 101 |
| Total | 196 ft | 26 | 30 - 2 corners = 28 | 430 |
With 3 rails per section that is 78 rails. The gate itself, its frame and hinges are not counted: build or buy it to fit the opening.
Fence post spacing
Posts are usually set 8 ft apart, center to center, so one 8 ft rail spans each section. That is common practice, not a rule, so the spacing is yours to change. Closer posts mean more posts but stiffer sections, which can help on a tall fence or with heavy boards. The calculator never stretches a section past your spacing: where a run does not divide evenly, every section in it comes out a little shorter.
Rails per section are also a choice. A common pattern is 2 rails (top and bottom) on fences up to about 4 ft and 3 rails on taller ones, and the calculator fills that in when you leave the box blank. We did not find a maker's or extension service's rule for it, so type the number your design uses.
How many pickets for a fence?
Pickets = fence length / the width each picket covers, rounded up for each run. A 1x6 picket is not 6 in wide. The American Softwood Lumber Standard, NIST's Voluntary Product Standard PS 20-20, lists a nominal 6 in board at a minimum dressed width of 5-1/2 in (140 mm) when dry, and a nominal 4 in board at 3-1/2 in (89 mm). Using 6 in would leave you short by about 1 picket in every 12.
| Style, 100 ft of fence | Each picket covers | Pickets |
|---|---|---|
| Privacy, 1x6 touching | 5.5 in | 1,200 / 5.5 = 218.2, so 219 |
| Spaced 1x6, 1 in gap | 5.5 + 1 = 6.5 in | 1,200 / 6.5 = 184.6, so 185 |
| Spaced 1x4, 2.5 in gap (4 ft picket fence) | 3.5 + 2.5 = 6 in | 1,200 / 6 = 200 |
| Board on board 1x6, 1 in overlap | 5.5 - 1 = 4.5 in | 1,200 / 4.5 = 266.7, so 267 |
These are minimum sizes, and the standard allows boards sold green (unseasoned) a slightly larger minimum, 5-5/8 in for a nominal 6, so measure a picket before you buy a large order. Each picket is as long as the fence is high. To price lumber by volume, the board foot calculator turns these sizes into board feet.
Board on board fence calculator
A board on board fence has two rows of pickets. The front row is spaced out and the back row covers the gaps, overlapping each front board on both sides. If the overlap on each side is o and the picket width is w, the front gap is w - 2o and each picket covers w - o of fence. With 1x6 pickets and a 1 in overlap the front gap is 3.5 in and each board covers 4.5 in, so the fence needs about 22% more pickets than a privacy fence of the same length. The overlap must be less than half the picket width, or there is no gap left to cover.
How much concrete per fence post?
The concrete figures follow QUIKRETE's data sheet for its Fast-Setting Concrete Mix (No. 1004). It says: Start by digging the post hole about 3 times the diameter of the post. Hole depth should be 1/3 the overall post height.
Its Setting Posts project sheet adds 6 in (150 mm) for the gravel base
, and the data sheet fills the dry mix to about 3 to 4 in from the top of the hole. The yields it gives are approximately 0.375 cu ft
for a 50 lb bag and 0.45 cu ft for a 60 lb bag.
If 1/3 of the post is in the ground, the depth is half the height above ground: a 6 ft fence needs 9 ft posts set 3 ft deep. The calculator works the concrete as the hole minus the post, from the gravel up to 3 in below the ground:
| Step, 4x4 post on a 6 ft fence | Working | Result |
|---|---|---|
| Hole | 3 x 3.5 in | 10.5 in wide |
| Depth | 36 in for the post + 6 in of gravel | 42 in |
| Concrete around the post | (3.1416 x 5.25 x 5.25 - 3.5 x 3.5) x 33 in | 2,453 cu in = 1.42 cu ft |
| Bags per post | 1.42 / 0.375 | 3.79 of 50 lb |
| 14 posts | 19.876 cu ft / 0.375 = 53.002 | 54 bags |
That is a lot of concrete, because a 3 ft deep, 10.5 in hole is big. QUIKRETE's own smaller example says two 50 lb bags will set a 3 in (75 mm) square post in a 9 in (225 mm) diameter hole 30 in (0.75 m) deep
; worked by volume the same way, that hole takes about 2.3 bags, so expect the calculator to round a little on the generous side. Type a narrower hole or a shallower depth if your local practice uses one, but in cold areas the post should go below the frost line, so check with your local building department. For a footing or slab, use the cubic yard calculator.
Fence calculator cost with your own prices
Prices vary by region, wood and season, so the calculator does not guess them. Open Your prices and type what your supplier charges per picket, post, rail and bag. To show the sum with made-up prices (not real ones: use your own), the 100 ft straight fence at 3.10 per picket, 18 per post and 6.50 per rail comes to 219 x 3.10 + 14 x 18 + 39 x 6.50 = 678.90 + 252 + 253.50 = 1,184.40, before concrete, screws or nails, hardware, the gate and any waste. We did not find a maker's figure for fasteners per picket, so they are not counted.
In Excel or Google Sheets
With the run length in feet in A2, the post spacing in B2 and the picket width in inches in C2:
Posts: =ROUNDUP(A2/B2, 0)+1
Pickets: =ROUNDUP(A2*12/C2, 0)
Microsoft's help page says ROUNDUP "Rounds a number up, away from 0 (zero)", and Google's says it rounds "always rounding up to the next valid increment". Add 1 post for each gate and work each run on its own row.
Questions and answers
How many fence posts do I need for 100 feet?
With posts 8 ft apart, 100 / 8 = 12.5 sections, rounded up to 13, so 14 posts for one straight run. Add 1 post for each gate, and take 1 off for each corner shared with another run.
How many pickets do I need for a 6 ft privacy fence?
Divide the fence length in inches by the actual picket width. A 1x6 picket is 5-1/2 in wide, so 100 ft needs 1,200 / 5.5 = 218.2, or 219 pickets, each 6 ft long.
How deep should fence posts be?
QUIKRETE's data sheet says hole depth should be 1/3 the overall post height, so a 6 ft fence needs 9 ft posts set 3 ft deep, plus 6 in of gravel underneath. Go below the frost line where the ground freezes, and check local rules.
How many bags of concrete per fence post?
It depends on the hole. A 4x4 post in a 10.5 in hole 3 ft deep takes about 3.8 bags of 50 lb fast-setting mix by volume. QUIKRETE says two 50 lb bags set a 3 in square post in a 9 in hole 30 in deep.
How many rails does a fence need?
A common pattern is 2 rails per section on fences up to about 4 ft and 3 rails on taller fences. It is common practice, not a rule, so the calculator lets you type your own number.
Does the calculator count the gate?
It counts the extra post each gate needs and leaves the gate opening out of the pickets and rails. The gate itself, its frame, hinges and latch are not counted.
Sources
Checked on 13 October 2026. If a rule has changed, please tell us.
- NIST: Voluntary Product Standard PS 20-20, American Softwood Lumber Standard (Table 3, dressed sizes)
- QUIKRETE: Fast-Setting Concrete Mix (No. 1004) product page
- QUIKRETE: Fast-Setting Concrete Mix data sheet (yield, hole size and depth)
- QUIKRETE: Setting Posts project sheet (gravel base)
- Microsoft Support: ROUNDUP function
- Google Docs Editors Help: ROUNDUP