What Size Fence Posts To Use

When installing a fence, choosing the correct fence post size is just as critical as selecting the fence panels themselves. At Abington Fencing, we know that the durability, stability, and safety of your fencing structure depend heavily on matching the right post size with your panel height and thickness. This guide explains in detail the appropriate post dimensions for various fencing requirements—whether you’re installing garden fencing, security fencing, or agricultural boundaries.

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Understanding Fence Post Sizing: Height, Thickness, and Depth

Fence posts serve as the backbone of any fencing system. The two main sizing factors to consider are:

• Post Height: How tall the post should be above ground to support the panel.

• Post Thickness: How wide and deep the post must be to bear the weight and wind load of the panel.

You must also consider how deep to set the posts into the ground, typically 1/3 of the total post length for maximum stability.

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Post Size for 3ft (0.9m) Fence Panels

• Ideal Post Height: 5ft (1.5m)

  • This includes 2ft in-ground depth.

• Recommended Post Thickness:

  • 75mm x 75mm (3” x 3”) for lightweight panels

  • 100mm x 100mm (4” x 4”) for heavier decorative or timber panels

This configuration works well for low garden borders or decorative fencing that’s not intended for security.

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Post Size for 4ft (1.2m) Fence Panels

• Ideal Post Height: 6ft (1.8m)

• Recommended Post Thickness:

  • 100mm x 100mm (4” x 4”)

At this height, wind resistance begins to play a larger role. We recommend concrete or pressure-treated timber posts for greater longevity and firmness.

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Post Size for 5ft (1.5m) Fence Panels

• Ideal Post Height: 7ft (2.1m)

• Post Thickness:

  • 100mm x 100mm (4” x 4”) minimum

  • Increase to 125mm x 125mm (5” x 5”) for composite or heavy hardwood panels

Posts must be driven or set in at least 2ft (60cm) deep, and use concrete fixing for added resilience.

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Post Size for 6ft (1.8m) Fence Panels

• Ideal Post Height: 8ft (2.4m)

• Recommended Thickness:

  • 125mm x 125mm (5” x 5”)

  • Especially important if using dense panels or in exposed/windy areas

6ft fencing is common for privacy and security. For this reason, it’s essential to use strong, thick posts and set them in at least 2.5ft of concrete footing.

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Post Size for 7ft (2.1m) Fence Panels

• Ideal Post Height: 9ft (2.7m)

• Post Thickness:

  • 125mm x 125mm (5” x 5”) minimum

  • Consider 150mm x 150mm (6” x 6”) for high-wind regions

This height is suitable for commercial fencing, high privacy, or noise reduction panels. The posts must be secured using deep concrete foundations (2.5–3ft) and possibly with cross bracing.

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Post Size for 8ft (2.4m) Fence Panels

• Ideal Post Height: 10ft (3m)

• Post Thickness:

  • 150mm x 150mm (6” x 6”) minimum

  • Required for heavy duty or composite panels

Fencing at this height requires engineering-grade support, especially if the fencing is part of a security perimeter. Consider steel posts or reinforced concrete for absolute stability.

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Choosing Between Wooden, Concrete, and Metal Fence Posts

Wooden Fence Posts

• Cost-effective

• Available in various sizes

• Should be pressure-treated to prevent rot

• Ideal for garden and residential fencing

Concrete Fence Posts

• Extremely durable

• Maintenance-free

• Ideal for tall fencing or sloped gardens

• Pair well with gravel boards

Metal Fence Posts

• Strongest option

• Best for security fencing

• Require corrosion protection or galvanisation

• Great for industrial or agricultural use

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Depth Guide for Fence Posts

Regardless of the height, the general rule is:

Fence post depth should be 1/3 of the total length of the post.

Always use post mix concrete or ballast and cement to ensure maximum grip and resistance.

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Gravel Boards and Their Impact on Post Sizing

Gravel boards (typically 6 inches or 150mm) elevate the panel off the ground to avoid rot and water damage. If you’re using a gravel board, add its height to your fence panel when calculating post height.

Example:
For a 6ft panel + 6” gravel board → Use an 8ft 6” post minimum

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Fence Post Spacing and Placement Tips

• Standard spacing: One post every 6ft (1.83m)—matching most UK panel widths

• Use string lines for accuracy

• Always check for underground utilities before digging

• Set posts using a spirit level to ensure vertical alignment

• Allow concrete to cure for 24–48 hours before attaching panels

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Wind Load and Terrain Considerations

For fencing installed in exposed areas, such as coastal or open countryside, opt for:

• Thicker posts (at least 125mm x 125mm)

• Deeper foundations (up to 3ft)

• Cross-braced corner posts or steel reinforcements

In sloped gardens, stagger post heights accordingly, or use stepped panel installations with precise measurements to maintain both aesthetics and function.

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Summary Table: Post Size by Fence Height

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Conclusion

Choosing the correct fence post size for your fencing height and thickness isn’t just a matter of looks—it’s essential for long-term stability, safety, and durability. At Abington Fencing, we recommend using the highest quality materials and following industry-standard guidelines to ensure your fence stands strong against time and weather.

If you’re unsure, speak to our experts—we’re here to advise on installation, materials, and custom fencing needs for both domestic and commercial projects.