Fence Picket Calculator

Fence dimensions
Posts and rails
Concreting
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mm
mm
mm
mm
mm
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mm
pcs.

Results

Fence pickets

pcs.
m
m

Posts and spans

pcs.
pcs.
mm
mm
m
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m
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About Fence Picket Calculation

The results are approximate. Before use, verify the calculations against the applicable standards and consult a specialist. The developer is not responsible for the consequences of use without project verification.

The Fence Picket Calculator determines the number of vertical pickets, support posts, spans and horizontal rails needed to build a fence. It calculates the required lengths of materials and the volume of concrete for individual post footings or a continuous strip foundation.

The fence picket calculation uses the overall fence dimensions, the width of each picket, the spacing between pickets and the selected post spacing. The results can be used to estimate material requirements and plan purchases.

Guidelines and recommendations

Calculating the number of pickets

Number of pickets. This is calculated from the total fence length, the width of one picket and the gap between adjacent pickets. First, the pitch is determined by adding the picket width and the gap. The calculation then finds the maximum number of whole pickets that fit along the given length.

Np = ⌊(1000 × L + g) / (b + g)⌋

Here, L is the fence length in metres, b is the picket width in millimetres and g is the gap between pickets in millimetres. The symbols ⌊ ⌋ mean rounding down to a whole number. Only the gaps between adjacent pickets are included, with no mandatory gap at the ends of the fence.

For example, with a fence length of 20 m, a picket width of 100 mm and a gap of 120 mm, the result is 91 pickets. The number is calculated for the entire fence length without splitting it into individual spans or subtracting post widths.

Picket length. The length of one vertical picket is the difference between the fence height and the ground clearance. The result is converted from millimetres to metres.

lp = (H - a) / 1000

Here, H is the fence height in millimetres and a is the ground clearance in millimetres. The total length of picket material is calculated by multiplying the number of pickets by the length of one picket.

Lp = Np × lp

Calculating posts and spans

Number of spans. The fence length is converted into millimetres and divided by the specified post spacing. The result is rounded up to a whole number so that the spacing between neighbouring posts does not exceed the selected value. The number of posts is one more than the number of spans.

Nspan = ⌈1000 × L / s⌉

Npost = Nspan + 1

Here, s is the specified post spacing in millimetres. The symbols ⌈ ⌉ mean rounding up to a whole number. The calculation assumes a straight fence section with a post at each end.

Equal spacing. When equal spacing is enabled, the entered spacing is treated as the maximum permissible value. After the number of spans is determined, the entire fence length is divided equally between them.

sequal = 1000 × L / Nspan

When equal spacing is disabled, most spans retain the specified spacing, while the last span takes up the remaining length. If that remainder is smaller than the main spacing, its length is shown separately.

For example, a fence 23 m long with a specified spacing of 2500 mm requires 10 spans and 11 posts. Without equal spacing, there are 9 spans of 2500 mm and one final span of 500 mm. With equal spacing, all 10 spans are 2300 mm long.

Post length. The above-ground height of the post is added to its embedment depth. The resulting length of one post is multiplied by the total number of posts.

lpost = (habove + hembed) / 1000

Lpost = Npost × lpost

The post height is specified independently of the fence picket height. The posts may therefore end above or below the top edge of the fence.

Calculating horizontal rails

Total rail length. This is calculated by multiplying the fence length by the number of horizontal rows. The calculator allows 2 or 3 rows of rails.

Lrails = L × n

Here, L is the fence length in metres and n is the number of rail rows. For example, a 20 m fence requires 40 m of rails in two rows or 60 m in three rows. The total is based on the full length of each row without additional allowances for joints or cutting.

Calculating concrete volume

Rectangular footings. A separate rectangular footing is assumed for each post. The volume of one footing is its length multiplied by its width and depth, then multiplied by the number of posts.

Vrect = Npost × a × b × h / 109

Circular footings. The volume of one cylindrical footing is based on the area of a circle and the footing depth. The calculation uses π ≈ 3.14159.

Vround = Npost × π × D2 × h / (4 × 109)

Continuous strip foundation. The concrete is calculated as a continuous rectangular strip along the full fence length. Its volume does not depend on the number of posts.

Vstrip = L × b × h / 106

In all formulas, V is the volume of concrete in m3, h is the footing depth in millimetres, and b is the footing width in millimetres. For a rectangular footing, a is its length in millimetres, while D is the diameter in millimetres for a circular footing. In the strip foundation formula, L is the full fence length in metres.

Concrete volume is calculated from the full geometric dimensions of the footings, without deducting the volume occupied by the embedded portions of the posts. Footing depth is entered independently of post embedment depth. No extra concrete allowance is included.

Calculation precision and assumptions

  • The numbers of pickets, posts and spans are whole numbers.
  • Dimensions in millimetres are displayed rounded to 1 mm. Intermediate calculations are performed without rounding.
  • Material lengths are displayed in metres to 0.001 m, and concrete volumes to 0.001 m3.
  • No material waste allowance is applied. The calculated extra allowance is 0%.
  • Pickets are counted across the entire fence length without splitting the fence into spans or accounting for post widths.
  • Geometric concrete volumes are calculated without additional loss factors.

European standards

The following European standards may be relevant when choosing the dimensions of a fence and its supporting structure:

  • EN 1991-1-4 (Eurocode 1). Actions on structures. Wind actions. Used to determine wind loads on fences and their supports.
  • EN 1993-1-1 (Eurocode 3). Design of steel structures. General rules and rules for buildings. Applicable when checking the strength and stability of metal components.
  • EN 1997-1 (Eurocode 7). Geotechnical design. General rules. Contains provisions for designing foundations with regard to ground conditions.
  • EN 206-1:2026. Concrete. Specification, performance, production and conformity. Part 1. Applicable when selecting concrete properties.

These standards provide technical guidance when designing a fence. The calculator does not apply code-based load or resistance factors to its geometric calculations.

FAQs

Why might the calculated number of pickets differ from the actual quantity used during installation?

The fence picket calculator determines the number of pickets for a continuous layout along the entire fence length. If the pickets are installed separately in each span, end gaps and post widths may change the required quantity. For this arrangement, it is advisable to check the layout of one span and the number of pickets in each section.

How do I calculate pickets for a double-sided, staggered fence?

For a double-sided staggered arrangement, enter the required gap between pickets in one row. Multiply the resulting number of pickets by 2 because the fence is filled on both sides. This method assumes the same number of pickets on each side.

What post spacing is suitable for a picket fence?

For preliminary calculations, a post spacing of about 2.0-2.5 m is commonly used. The appropriate value depends on the fence height, post material and cross-section, wind exposure and soil conditions. Equal spacing produces identical spans without exceeding the selected maximum spacing.

How many rows of horizontal rails should I use?

Relatively low fences often use 2 rows of horizontal rails. For taller fences or when additional picket fixing points are needed, 3 rows may be used. The final choice depends on picket dimensions, rigidity and fixing method.

Why can the calculated concrete volume differ from the amount actually used?

The fence calculator determines the geometric volume of rectangular, circular or strip footings. Actual consumption may differ because of uneven excavation sides, changes in excavation dimensions and the volume occupied by the installed posts. These factors should be considered separately when ordering concrete.