Fencing is priced by length, so the perimeter is the number that drives every other estimate: how many posts, how much wire or rail, and roughly what it will cost. This guide covers how to measure the perimeter, how to turn it into a materials list, and how to avoid the counting mistakes that leave you a few posts or half a roll short. A worked example for a two-acre paddock pulls it all together.
Step 1: Measure the perimeter
You can get the perimeter three ways. Each also gives you the length of individual sides, which you will need for counting posts.
| Method | How | Good for |
|---|---|---|
| Satellite map | Tap each corner of the field on imagery; the tool reports every side and the total | Fence lines and field edges visible from above |
| GPS walk | Walk the line with your phone recording; pause at corners | Planned lines that do not exist yet; edges hidden by trees |
| Tape or measuring wheel | Measure each side on the ground | Short runs, small yards, and checking a map measurement |
A few points apply whichever method you use:
- Measure the line where the fence will actually go. If the new fence sits a few feet inside the boundary to clear a ditch or hedge, measure that line, not the property line.
- Add points where the line bends. Two corners joined by a straight line will undercount a curved run.
- Allow for slope. Map and GPS distances are horizontal. On sloping ground the fence follows the surface and is a little longer: about 0.5% longer on a steady 10% grade and about 2% on a 20% grade. On gentle land the waste allowance covers this; on steep land add it explicitly.
For a GPS walk, the guide on walking a property boundary with GPS covers the field routine in detail. To check a single side between two known points, the distance between coordinates tool gives the length and bearing.
Step 2: Count the posts
Posts go at every corner and at regular intervals along each side. The key is to count per side, not from the total perimeter, so that every corner gets a post even when a side is not an exact multiple of the spacing.
For each side, the number of intervals is the side length divided by the spacing, rounded up. Then:
- Closed boundary (a fence that goes all the way around): posts = the sum of the intervals on all sides. Every post is the start of exactly one interval, so nothing needs adding.
- Open run (a fence with two ends, such as a single boundary line or a loop broken by a gate opening): posts = the sum of the intervals + 1 for each separate run, because a run has one more post than it has gaps.
Rounding up per side means the actual spacing on most sides ends up slightly shorter than your target. That is what you want: your chosen spacing is a maximum, and no gap exceeds it.
Choosing a spacing
Spacing depends on the fence type, the animals, the ground, and local practice. Barbed and high-tensile wire fences are often built with line posts somewhere around 10 to 16 feet apart, woven wire and board fences closer together, and electric fences on flat ground can go further. Treat those as rough ranges and follow your material supplier’s or extension service’s guidance for your situation.
The fence calculator applies the same per-side rule, so you can try different spacings quickly.
Step 3: Wire, rails, or mesh
For strand fencing, the material length is the fence length times the number of strands. For board fences, it is the fence length times the number of rails. Mesh or woven wire is usually a single run, so the material length is the fence length.
Leave out the gate openings: wire and rails stop at gate posts.
Then add a waste allowance for tying off at corners and gates, wrapping around end posts, splices, sag, and mistakes. Something in the range of 5 to 10% is a common starting point; use more for rough or steep ground or many short runs.
Material = fence length × strands × (1 + waste %)
Finally, round up to whole rolls or whole boards. Wire roll lengths vary by product and country (in the US, barbed wire is commonly sold in 1,320-foot, quarter-mile rolls), so check what your supplier stocks before dividing.
Step 4: Gates, corners, and bracing
Line posts are only part of the post order. The posts that take the strain are the ones at the ends of each straight pull.
- Corner posts carry the tension of two sides, so they are usually larger and set deeper than line posts.
- Gate posts carry the weight of the gate on one side and the wire tension on the other. They are usually the heaviest posts in the fence.
- Bracing stops end posts from leaning under wire tension. A common design is the H-brace: a second post set some distance in from the corner or gate post, joined to it by a horizontal rail and a diagonal tension wire. Corners are often braced in both directions.
Brace posts may replace the nearest line post or sit in addition to it, depending on your layout, so list them separately in your order rather than assuming they are included in the line post count. Long straight runs are also commonly braced partway along; ask your supplier how often for the wire and tension you are using.
Step 5: Estimate the cost
There are two ways to price a fence, and it helps to do both:
- By length: fence length × an all-in rate per foot or meter, from a contractor’s quote or your own past jobs.
- By materials: posts × price per post, plus wire rolls or boards, plus brace materials, gates, fasteners, and any hire or labor.
The per-length figure is quick for comparing options; the materials list is what you actually buy. Prices vary a great deal by region, material, and year, so use current local numbers rather than national averages. If your measurements are in meters and your quote is in feet, or the other way around, the distance converter handles the switch.
Worked example: a two-acre paddock
A rectangular paddock measures 330 ft × 264 ft. That is 87,120 sq ft, exactly 2 acres. It will get a 4-strand barbed wire fence with a target line post spacing of 10 ft and a 12-ft gate in the middle of one long side.
Perimeter and fence length
- Perimeter: 330 + 264 + 330 + 264 = 1,188 ft
- Fence length excluding the gate: 1,188 − 12 = 1,176 ft
Posts
The gate turns the loop into one open run from gate post to gate post. The gate side is split into two 159-ft pieces.
| Side | Length | Length ÷ 10 ft | Intervals (rounded up) |
|---|---|---|---|
| Gate side, left piece | 159 ft | 15.9 | 16 |
| Short side | 264 ft | 26.4 | 27 |
| Long side | 330 ft | 33 | 33 |
| Short side | 264 ft | 26.4 | 27 |
| Gate side, right piece | 159 ft | 15.9 | 16 |
| Total | 1,176 ft | 119 |
Posts = 119 intervals + 1 for the single open run = 120 posts: 4 corner posts, 2 gate posts, and 114 line posts. On the short sides the actual spacing works out to about 9.78 ft, just under the 10-ft target.
(Without the gate, as a closed loop, the count is 33 + 27 + 33 + 27 = 120 as well. The totals match here by coincidence of the numbers; with a different gate position or spacing they can differ by a post or two, which is why it pays to count per side.)
Add brace posts on top: for example, two per corner if each corner is braced in both directions and one per gate post, which is 4 × 2 + 2 × 1 = 10 more posts.
Wire
- 1,176 ft × 4 strands = 4,704 ft
- With a 10% waste allowance: 4,704 × 1.10 = 5,174.4 ft
- In 1,320-ft rolls: 5,174.4 ÷ 1,320 ≈ 3.92, so 4 rolls (5,280 ft, leaving about 106 ft spare)
That is a tight margin. If the ground is uneven or you expect to splice around obstacles, a fifth roll is cheap insurance.
Cost
Suppose your quote works out to an all-in rate of $4.50 per foot. That figure is only for illustration, not a market price. The fence would cost 1,176 × $4.50 = $5,292, plus the gate itself if the rate does not include it.
The same paddock in metric
A 100 m × 80 m paddock fenced as a closed loop with 3-m spacing needs 34 + 27 + 34 + 27 = 122 posts. With 3 strands and 5% waste, the wire comes to 360 m × 3 × 1.05 = 1,134 m.
Doing it on a phone
If you measured the field in the Land Measure app, Pro includes a fence and boundary estimator that turns a saved boundary into a post count, material length, and a cost at the rate you enter. For a quick estimate from side lengths, the free fence calculator on this site does the same arithmetic. Either way, walk the line before you order: a ditch, a rock outcrop, or a neighbor’s existing fence can change the plan, and the materials list with it.