How Much Postcrete Do You Need Per Fence Post?

Not sure how many bags of Postcrete per fence post you need? This guide gives you quick bag estimates for common post sizes and hole depths, plus an easy way to total it up for a full fence line. (You’ll also hear it called post mix or postmix concrete — same job, different wording.)

What we supply: we stock Birkdale FenceMate® Post Concrete (20kg) — a rapid-setting, “just add water” post concrete that’s ideal for fence posts and small-to-medium gate posts.

Quick answer: most standard domestic fence posts use 1.5–2 bags (20kg) each, while gate posts and heavy-duty closeboard often need 2–3+ bags depending on soil and exposure.

Why getting the right amount matters

• Too little post concrete and the post can rock, lean, or loosen over time.
• Too much and you’re wasting money (usually because the hole is wider than it needs to be).
• Correct depth, sensible hole width, and good compaction is what keeps fences standing.

Recommended Postcrete / Postmix bags per post (20kg)

These are practical “on-site” estimates that work well for most UK fencing. If your ground is very soft/sandy, you’re in an exposed spot, or you’re hanging a gate, use the higher end.

Pro tip: Round up. Having an extra bag on site is far cheaper than leaving posts half-set.

Hole size matters (this is what changes the bag count)

Two people can both install a “4×4 post” and use different amounts of Postcrete purely because one dug a wider hole. As a rough guide, these are common hole sizes and what they often consume:

Postcrete calculator: how many bags for a full fence line?

1. Count your posts. A run of 7 fence panels usually uses 8 posts (one more post than panels).
2. Pick your bags-per-post from the tables above.
3. Multiply and add a small margin for corners/gates.

Example: 8 posts × 2 bags = 16 bags total. Add 1–2 spare bags = 17–18 bags.

Corner posts, end posts, and gate posts: allow extra. These often need a wider hole and more concrete, especially if you’re aligning at an angle or taking hinge force from a gate.

Why Postmix beats mixing concrete (especially on a muddy site)

Ever tried to wheelbarrow a full barrow of wet concrete across a muddy building site? Not only is it exhausting, but one rut and one wobble is all it takes to end up face-first in the mud, covered in concrete… and suddenly questioning every life choice that led you to that moment.

Trust us — we’ve been installing fencing on building sites for years. That’s the real beauty of postmix (what most people search as “Postcrete”): you carry a 20kg bag to the hole, tip it in, add water, and crack on. No mixer, no ballast pile, and no accidental concrete spa treatment.

• Less mess: cleaner site, cleaner van, fewer arguments.
• Less kit: no mixer to drag out, fuel up, and clean.
• Faster setting: posts firm up quickly so you can keep moving.
• More consistent: every hole gets the same mix (instead of “that’ll do”).

If you’re setting loads of posts, mixing your own can be cheaper — but for most DIY jobs and everyday installs, postmix saves time, stress, and trousers.

How to use Birkdale FenceMate® Post Concrete (the fast-set method)

Birkdale FenceMate® is designed so you can set posts quickly with minimal mess. You don’t need separate cement and ballast.

1. Dig your hole and place the post. Check it’s straight with a level and brace it if needed.
2. Fill the hole to around 1/3 depth with clean water.
3. Pour the dry mix in evenly around the post until there’s no visible standing water.
4. Re-check the post is plumb and hold/brace it while it grabs.
5. Leave it to set. Rapid set products typically firm up quickly, but avoid heavy strain until fully cured.

Setting depth and stability tips

• Depth first: for most fencing, start at 600mm (2ft). Go deeper for tall, heavy or exposed fences.
• Widen the base slightly (a “bell” shape) for better grip in softer ground.
• Finish with a slope away from the post so rainwater sheds off (helps reduce rot at ground level).
• Consider a Post Saver sleeve at ground level (where timber posts usually fail first).

How deep should fence posts be set?

For most domestic fencing, 600mm (2ft) is a solid baseline. If you’re going taller, fitting closeboard in an exposed garden, or your soil is loose, increase to 750–900mm.

• Standard panels (4–6ft): ~600mm depth
• Heavy-duty / exposed / taller fencing: ~750mm depth
• Gate posts: 750–900mm depth (and usually a wider hole)

Postcrete vs postmix concrete: what’s the difference?

In everyday UK DIY/trade use, “Postcrete” is often used as the generic term people search, while postmix / post mix concrete is the descriptive name. They both refer to rapid-setting, ready-to-use post concrete. The important bit is choosing a quality 20kg bag and using the correct hole size and depth for your fence type.

FAQs

Is 1 bag of Postcrete enough per fence post?

Sometimes, but often not. For many 4×4 fence installs you’ll typically use 1.5–2 bags once you account for a proper hole size. If you’re unsure, round up — especially for corners and exposed sites.

How many bags of postmix concrete for gate posts?

Plan on 2–3+ bags per gate post. Gate posts take hinge force, so it’s worth overbuilding with a wider and/or deeper hole.

Can I use postmix for concrete posts as well as timber?

Yes — rapid-set post concrete is suitable for timber, metal and concrete posts. The method is the same: correct depth, keep it plumb, and let it cure.

Buy Birkdale FenceMate® Post Concrete (20kg)

We stock Birkdale FenceMate® rapid set post concrete 20kg — ideal for setting fence posts quickly and cleanly.

• Shop fencing supplies
• Fence posts
• Fence panels
• Contact us if you want us to sanity-check quantities

CE Clarke Fencing — supplying quality fencing and landscaping materials since 1984.