Picket Fence Calculator Australia: Cost & Materials

A picket fence calculator for Australia works out how much timber, paint, and budget you need for a new fence. You enter your fence length, height, picket width, and spacing, and it returns the number of pickets, rails, posts, and total material cost. This guide explains the formula, gives a worked example, and covers the common mistakes that lead to under-ordering or overspending.

Formula

The core formula for the number of pickets is:

Number of pickets = ceil( L / ( (W + S) / 1000 ) )

Where:

• L = total fence length in metres
• W = picket width in millimetres (convert to metres by dividing by 1000)
• S = gap between pickets in millimetres
• ceil() = round up to the nearest whole number

For posts: Number of posts = ceil(L / post spacing) + 1

For rails: Total rail length = L × 2 (assuming two horizontal rails per fence section).

Timber volume is estimated by summing the volume of pickets, posts, and rails. A typical picket is 19 mm thick, a post is 100 mm × 100 mm, and a rail is 100 mm × 50 mm. Add 600 mm to the post height for burying in concrete.

Worked Example

Using the default values from the calculator: fence length = 20 m, height = 1.2 m, picket width = 90 mm, gap = 30 mm, post spacing = 2.4 m.

1. Picket pitch = 90 mm + 30 mm = 120 mm = 0.12 m
2. Number of pickets = 20 / 0.12 = 166.67 → round up to 167 pickets
3. Number of posts = 20 / 2.4 = 8.33 → round up to 9, plus 1 = 10 posts
4. Rail length = 20 × 2 = 40 m
5. Picket volume = 167 × (0.09 × 1.2 × 0.019) = 167 × 0.002052 = 0.3427 m³
6. Post volume = 10 × (0.1 × 0.1 × 1.8) = 10 × 0.018 = 0.18 m³
7. Rail volume = 40 × (0.1 × 0.05) = 40 × 0.005 = 0.2 m³
8. Total timber volume = 0.3427 + 0.18 + 0.2 = 0.72 m³

The calculator shows 167 pickets, 10 posts, 40 m of rails, and 0.72 m³ of timber (rounded to two decimals).

How to Use the Calculator for Your Fence

Start by measuring the total length of the fence line in metres. Use a tape measure along the ground, not the slope – if the ground is uneven, measure along the actual surface and consider stepping the fence. Decide on the picket width (common sizes are 70, 90, or 100 mm) and the gap between pickets (often 20–50 mm). The gap affects privacy and wind resistance. For a standard 1.8 m high fence, posts are usually spaced 2.4 m apart, but check with your local council – some areas require closer spacing in high-wind zones.

Enter your figures and the calculator gives you the number of pickets, posts, rail length, and total timber volume. Use the timber volume to estimate cost by multiplying by the price per cubic metre from your local timber supplier. For a more accurate cost, call a supplier and ask for a quote based on your exact dimensions.

Choosing the Right Picket Size and Spacing

The picket width and gap determine the look and function of your fence. A narrow gap (20 mm) gives more privacy and is better for keeping small pets in. A wider gap (50 mm) lets more light through and reduces wind load, which is important in coastal areas. Common Australian styles include:

• Paling fence – 100 mm pickets with a 20 mm gap, often used for backyards
• Bali style – 90 mm pickets with a 30 mm gap, popular for a modern look
• Closed picket – no gap, maximum privacy but uses more timber

For height, the standard is 1.8 m for side and back fences, but front fences are often lower (1.2 m) to maintain street visibility. Check your local council regulations – some limit front fence height to 1.2 m without a permit.

Common Mistakes and How to Avoid Them

The most common error is mixing units. Picket width and gap are usually given in millimetres, but fence length is in metres. Always convert to the same unit – divide millimetres by 1000 to get metres. Another mistake is not rounding up the number of pickets. You can’t buy a fraction of a picket, so always round up to the next whole number. If you have a corner or an end post, you may need an extra post – count them carefully. Also, remember to add 600 mm to the post length for the part buried in concrete. Finally, timber volume is an estimate – actual volume depends on the exact dimensions of the timber you buy, which may be slightly larger or smaller than nominal sizes.

Cost Factors in Australia

Material costs vary by region and timber type. Treated pine is the most common and economical choice, while hardwood (like ironbark or merbau) is more expensive but lasts longer. In 2025, treated pine pickets (90 mm × 19 mm × 1.8 m) typically cost between $3 and $5 each, while hardwood pickets can be $8–$12 each. Posts (100 mm × 100 mm) cost around $15–$25 for treated pine and $30–$50 for hardwood. Concrete for post holes adds about $5–$10 per post. Labour costs, if you hire a contractor, are usually $80–$150 per metre installed. To get an accurate total, use the calculator to get the number of pickets and posts, then multiply by local prices.

Safety and Installation Tips

Check for underground services (water, gas, electricity) before digging post holes – call Dial Before You Dig (now called “Before You Dig Australia”) for a free location service. Wear gloves and safety glasses when cutting timber, and use a dust mask if sawing treated pine. For post holes, dig at least 600 mm deep and fill with concrete – ensure the post is plumb (vertical) using a spirit level. Space posts evenly along the fence line, and attach rails with galvanised nails or screws to prevent rust. If you’re building a fence over 1.8 m high, you may need a building permit – check with your council. Always allow for expansion and contraction of timber in the Australian climate.

Frequently Asked Questions

How many pickets do I need for a 50 metre fence?
Using the default picket width of 90 mm and gap of 30 mm, each picket covers 120 mm (0.12 m). So 50 / 0.12 = 416.67, round up to 417 pickets.

What is the standard gap between pickets?
There is no single standard – it depends on your preference and local rules. Common gaps are 20 mm for privacy, 30 mm for a balanced look, and 50 mm for a more open fence.

Do I need a permit to build a picket fence in Australia?
Most councils require a permit for fences over 1.8 m high, and some require one for any front fence. Check your local council’s website or call them to confirm the rules for your property.

What is the best timber for a picket fence in Australia?
Treated pine is the most popular because it’s affordable and resistant to rot and termites. Hardwood is more durable and looks better but costs more. Cypress pine is another option that’s naturally termite-resistant.

How deep should fence posts be?
A common rule is to bury at least one-third of the post height, but for a 1.8 m fence, 600 mm is typical. In soft soil, go deeper – up to 900 mm. Always set posts in concrete for stability.

Can I use the calculator for a curved or sloped fence?
The calculator assumes a straight, level fence. For a sloped block, you may need to step the fence – each step requires an extra post and possibly longer pickets. Measure the actual length along the slope and add 5–10% for waste.

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in L | Fence length | m | 20 | 1
in H | Fence height | m | 1.2 | 0.5
in W | Picket width | mm | 90 | 20
in S | Gap between pickets | mm | 30 | 0
in P | Post spacing | m | 2.4 | 0.6
out n | Number of pickets | - | ceil(L / ((W + S) / 1000)) | 0
out posts | Number of posts | - | ceil(L / P) + 1 | 0
out rails | Rail length | m | L * 2 | 1
out timber | Timber volume | m³ | (n * W / 1000 * H * 0.019) + (posts * 0.1 * 0.1 * (H + 0.6)) + (rails * 0.1 * 0.05) | 2