Measure the fence line
Enter the total straight length in m, cm or mm, the number of runs, the height and the post spacing between centres.
Australian metric calculatorStart with your measurements
Fence calculator Australia
Use this fencing calculator to estimate posts, rails, palings, pickets, sheets or panels and post-hole concrete for a straight timber, Colorbond or picket fence. Enter the length in metres, centimetres or millimetres, set the post spacing and choose a waste allowance.
How many fence posts do I need?
Divide the fence length by the post spacing and round up to get the number of sections, then add one end post per straight run. For example, a 20 m fence at 2.4 m spacing needs 9 sections and 10 posts.
✓ m, cm or mm inputs✓ Posts, rails, infill and concrete✓ Transparent formula
How to use the fence calculator
From fence line to a material list
Work through the three steps. Measure each straight run separately, then add the lengths together. Post spacing, product sizes and rail counts vary by product, so confirm them with your supplier.
Choose the infill
Pick timber palings, pickets, steel sheets or pre-made panels and enter the face width and gap, or the panel width.
Add concrete and cost
Optionally add the post-hole size and a concrete bag yield, plus per-unit prices for an indicative material cost.
Fence planning answers
Common fence calculator questions
These answers explain the measurements and product details behind the estimate. The calculator keeps your exact result and rounding visible.
How many fence posts do I need?
Divide the fence length by the post spacing and round up for the number of sections, then add one end post for each straight run. A 20 m fence at 2.4 m spacing is 9 sections and 10 posts. Each gate opening adds two posts.
How do I calculate palings for a fence?
Divide the fence length by the paling face width plus any gap, then round up. Add a waste allowance for cuts and breakage. With 100 mm butted palings, a 20 m fence needs 200 palings before waste.
What post spacing should I use?
Many Australian timber paling and Colorbond fences use 2.4 m post centres, but the correct spacing depends on the product, panel size, height and site. Confirm it with the manufacturer or installer.
How much concrete per fence post?
The concrete per hole is the hole volume, π × (diameter ÷ 2)² × depth, minus the embedded post. A 200 mm wide, 600 mm deep hole, typical for a 1.8 m timber fence, is about 0.019 m³ before subtracting the post.
How many bags of concrete per post?
Divide the concrete volume per hole by the yield of one bag and round up. A 20 kg premix bag yields roughly 0.011 m³, so a 0.019 m³ hole is about two bags. Use the yield printed on your bag.
Does it work for Colorbond, timber and picket fences?
Yes. Choose timber palings, pickets, steel sheets or pre-made panels and enter the product dimensions. Panels are counted as whole units and add one post per panel join.
What about corners and sloped ground?
Measure each straight run separately and add them as one total length with the matching number of runs. The estimate does not model corners, curves, stepped panels or raked ground.
Does the estimate include gates, caps and labour?
Gate openings adjust the infill length and add gate posts, but gate hardware, post caps, fasteners, delivery and labour are not included. Pool and boundary fences also have legal requirements this tool does not check.
Methodology
How the fence estimate is calculated
The fence length is normalised to metres, the calculator keeps full precision during calculation and always rounds posts, rails, infill units and concrete bags up to whole units.
Count the sections
Divide the fence length by the post spacing and round up.
sections = ceiling(fence length ÷ post spacing)Count the posts
Add one end post per run, plus two posts per gate opening.
posts = sections + runs + (2 × gates)Count the rails
Two rails up to 1.2 m high, otherwise three, unless you set it.
rail pieces = sections × rails per sectionCount the infill
Divide the fill length by one unit's width plus its gap.
infill units = ceiling(fence length ÷ (width + gap))Add the waste allowance
Apply the percentage for cuts and breakage, then round up.
infill ordered = ceiling(infill units × (1 + waste ÷ 100))Estimate the concrete
Use the hole volume per post, then divide by the bag yield.
concrete per hole = π × (diameter ÷ 2)² × depth; bags = ceiling(total concrete ÷ bag yield)Verified examples
Regression-tested calculations
These fixed cases are checked by the automated formula test suite so rounding and unit conversion changes cannot pass unnoticed.
| Scenario | Key inputs | Verified result |
|---|---|---|
| Posts and rails for a straight run | 20 m, 2.4 m spacing, 1 run, 1.8 m high | 9 sections, 10 posts, 3 rails per section, 27 rail pieces |
| Butted timber palings | 20 m, 100 mm palings, 0 mm gap, 10% waste | 200 palings before waste, 220 palings ordered |
| Pre-made panels | 20 m, 2,400 mm panels, 1 run | 9 panels and 10 posts |
| Post-hole concrete | 10 posts, 200 mm × 600 mm holes, 0.011 m³ per bag | 0.188 m³ of concrete, 18 bags |
| Gate opening | 20 m with one 1.0 m gate opening | 19 m of infill and two extra gate posts |
Worked example
A 20 m paling fence at 2.4 m spacing
A 20 m, 1.8 m high paling fence needs 10 posts and 27 rail pieces. With 100 mm butted palings and 10% waste, that is 220 palings. With 200 × 600 mm post holes at 0.011 m³ per bag, allow about 0.19 m³ of concrete, or 18 bags.
- Posts
- 10
- Palings (with 10% waste)
- 220
- Concrete
- 18 bags
What this estimate includes
- Straight-run posts, rails and infill units
- Timber, picket, steel-sheet or panel infill
- Your selected infill waste allowance
- Optional post-hole concrete and per-unit material cost
What it does not include
- Corners, curves, stepped or raked panels and sloped ground
- Gate hardware, caps, fasteners, delivery and labour
- Engineered wind, bushfire (BAL) or retaining design
- Pool-barrier (AS 1926) and boundary-fence legal requirements
Sources and review record
| Calculation rule | Supporting source | Formula version | Checked date |
|---|---|---|---|
| Equations, rounding and expected results | Formula specification v1.0 and automated acceptance tests | 1.0 | |
| Post spacing 2.4 m and rail count for a 1.8 m fence | Narangba Timbers | 1.0 | |
| Colorbond panel width and heights | Colorbond panel sizes (installer) | 1.0 | |
| Post-hole size and premix concrete bag yield | Outback Fencing,BCSands | 1.0 |
Default product dimensions are typical starting values only. Confirm post spacing, product sizes, rail counts and concrete yield with your supplier. Recheck quarterly and whenever a source, formula, rounding rule or supplier convention changes.