How Deep Should a Fence Post Be?

Learn how deep to set a fence post for maximum strength and stability. This guide covers ideal post depths, Postcrete usage, and key factors like soil type, wind exposure, and sloped ground — plus a link to our full installation guide.

Wooden Fence Post

Concrete Fence Posts

The Simple Rule of Thumb

As a general guide, your fence post should be buried at least one-third of its total length in the ground — and never less than 600mm (2ft) deep.

Fence Height	Recommended Post Length	Depth in Ground
0.9 m (3 ft)	1.5 m	0.6 m
1.2 m (4 ft)	1.8 m	0.6 m
1.8 m (6 ft)	2.4 m	0.6m
2.1 m (7 ft)	2.7 m	0.6-0.8m

This ratio gives the best balance between fence height and ground stability, especially in areas prone to wind or soft soil.

👉 For a full installation walkthrough, see our complete guide:
How to Install a Wooden Fence Post – Step-by-Step

Why Post Depth Matters

The deeper your post is set, the stronger and more stable your fence will be. Proper depth prevents:

Leaning or movement in high winds
Post lift during winter frost cycles
Soil pressure failure when retaining small ground differences
Uneven alignment on sloped ground

Posts that are too shallow will eventually loosen or tilt, especially on heavy or wind-loaded fences like closeboard and solid panels.

Accounting for Slopes and Uneven Ground

If your fence runs along a slope or stepped garden, dig deeper on the higher side of each post to compensate for the drop.
This keeps the fence line level across the top and prevents exposed gaps at the base.

Closeboard Fence Panels

As a rule:

Add 100–150 mm of extra depth on steeper sections.
Ensure posts are buried evenly in relation to the lowest ground level, not just surface height.
For very uneven terrain, consider staggered post heights or a stepped fencing layout using gravel boards for a neat finish.

Proper depth on slopes also counteracts the downward force of retained soil pushing against lower panels.

How Much Postcrete to Use

For most domestic fencing, use 1.5–2 bags of Postcrete per post.

Rapid Set Post Concrete

Post Size	Hole Depth	Postcrete (20 kg Bags)
75 mm × 75 mm (3″)	600 mm	1–1.5 bags
100 mm × 100 mm (4″)	600–750 mm	1.5–2 bags
125 mm × 125 mm (5″)	600–900 mm	2-3 bags

Pro tip: Dig holes 50–100 mm wider than the post to allow the Postcrete to surround the timber evenly, locking it in place and improving drainage.

Other Key Factors

1. Wind Exposure

In open or coastal areas like Suffolk, choose deeper holes — up to 900 mm for 6 ft fences — to resist uplift and sway.

2. Soil Type

Clay soils are firm but hold water — slope concrete tops away from posts to shed rain.
Sandy soils are loose and need deeper holes with extra Postcrete.
Rocky or chalk soils offer high grip but can limit digging depth; wedge posts securely.

3. Fence Weight and Design

Heavier fences such as closeboard panels or decorative screens catch more wind.
If you’re using concrete gravel boards include this in your total finished fence height.

Quick Reference

Fence Height	Minimum Depth	Bags of Postcrete	Notes
0.9 m (3 ft)	600 mm	1 bag	Light picket or boundary fencing
1.2 m (4 ft)	600 mm	1–1.5 bags	Garden borders
1.8 m (6 ft)	600–750 mm	1.5–2 bags	Standard garden fences
2.1 m (7 ft)	600-750 mm	2 bags	Heavy-duty or exposed sites