Red: the default UK wall plug
If a British toolbox has one bag of wall plugs, they’re red. The red plug is the general-purpose household fixing — the one merchants stock deepest, and the one most bags of “assorted” plugs are mostly made of. It takes a 6 mm hole and a screw around 3.5–5.0 mm — a No.8 / 4 mm wood screw is the typical partner.
The question most red-plug searchers actually have is “is red enough?” For everyday indoor fixings — shelf brackets, curtain rails, towel rails, mirrors, small cabinets — the answer is usually yes: a red plug in solid brick holds around 20 kg per fixing, and most of those jobs spread the weight across two or more fixings. The trade rule of thumb: if you’re unsure between yellow and red, use red. Only step up to brown when the load is genuinely heavier — loaded shelving, kitchen wall units, or curtain poles carrying thick, lined drops.
The one rule that stops most failures
The drill bit matches the plug; the screw is 1–2 mm smaller than the bit. A red plug wants a 6 mm hole, a brown plug a 7 mm hole, and the screw bites the plug and expands it against the wall. Get it backwards — an oversized hole, or a screw too fat — and the plug spins or splits before it grips. Colour-to-size is a common UK convention, not a guaranteed standard, so it still varies a little by brand: check the packaging, which prints the bit and screw sizes.
Fitting it so it holds
- Use the exact bit size — don’t oversize. The number-one failure is a hole that’s too big, so the plug spins. If it’s already too big, go up a plug size, or fill and re-drill.
- Depth beats width. In brick with voids go longer, not wider — width invites splitting, length adds grip.
- Drill slightly deeper than the plug and clear the dust before inserting it — packed dust stops the plug seating and causes pull-out.
- Drill the brick, not the mortar joint, and get past the plaster into the brick or block behind — a plug gripping only the plaster skim pulls straight out.
- Use a hammer drill and a carbide masonry bit — brick and block need percussion. Not sure which bit? See the masonry drill bit guide, and the size converter for mm ↔ imperial.
When a wall plug is the wrong fixing
Never in plasterboard. A wall plug needs solid material to expand against; in hollow plasterboard it just spins and tears out. On a stud wall or ceiling, use a drywall anchor instead — a different fixing for a different wall.
Above roughly 50 kg per fixing, step up from plastic. Past that, a plastic plug is the wrong tool — move to a steel sleeve anchor or another concrete anchor sized for the load. It’s about picking the right fixing, not fine print.
Common questions
What size drill bit for a red wall plug?
A 6 mm drill bit. Red is the UK default wall plug (rawlplug): drill a 6 mm hole with a carbide masonry bit in a hammer drill, and pair it with a screw around 3.5–5.0 mm. The bit matches the plug and the screw is 1–2 mm smaller than the bit. Red holds roughly 20 kg per fixing in solid brick as an indicative maximum — check the plug packaging, since colour sizing varies a little by brand.
What screw fits a red rawlplug?
A screw around 3.5–5.0 mm in diameter — a No.8 (about 4 mm) is the typical choice, and a No.10 is the upper end. The key is that the screw is 1–2 mm smaller than the 6 mm drill bit, so it bites into the plug and expands it against the wall. Too fat and it splits the plug; too thin and it never expands enough to grip. The screw needs to be long enough to pass through your fixture and reach at least the full length of the plug.
How much weight can a red wall plug hold?
Around 20 kg per fixing in solid brick — but treat that as an indicative maximum, not a rated spec. Real capacity depends on the substrate (weaker, older or aerated block holds much less), how deep the screw engages, and how well it's installed. Crucially it's PER FIXING POINT: most fixtures use two or more plugs, so divide the item's weight between them and leave margin — a good rule is to size each plug for about 1.5× the load it will actually see. Use at least two fixings for anything over about 10 kg.
Red or brown wall plug — which do I need?
Red is the default for general household fixings; brown is the step-up for heavier everyday loads. Work it out per fixing, not per fixture: divide the weight by the number of plugs, then add margin. Red holds ~20 kg per fixing and suits a No.8 screw; brown holds ~25 kg and takes a fatter No.10. For shelf brackets, curtain rails and mirrors, red is plenty; for kitchen wall units, loaded shelving or heavy curtain poles, use brown. When you're on the fence, size up. See the full red-vs-brown breakdown on the brown wall plug page.
Why does my red wall plug spin?
Almost always because the hole is too big. If you drilled oversize, the bit wandered, or the plug is sitting in soft mortar or a plaster skim rather than solid brick, it turns instead of gripping. Fixes: use the exact 6 mm bit (don't oversize), go up to a brown plug if the hole is already too large, or fill the hole and re-drill. Drill into the brick itself — not the mortar joint — get past any plaster into the brick behind, and clear the dust before pushing the plug in.
Where these numbers come from
The red-plug sizing here — a 6 mm bit, a 3.5–5.0 mm screw, and an indicative ~20 kg per fixing in solid brick — is cross-referenced across UK fixing suppliers and manufacturer references (Rawlplug, Screwfix, Toolstation and UK trade guides), which are unanimous on red = 6 mm. Load figures are indicative maxima in solid brick and vary between sources, so they’re guidance, not rated specifications, and colour sizing is a widely-followed convention rather than a formal standard — the packaging is the final word. For structural or safety-critical fixings, follow the manufacturer’s data and step up to an engineered anchor.
Wall-plug sizing here is common-convention UK guidance for light-to-medium DIY fixings. Colour coding and load figures vary by brand — always follow the plug packaging. Loads are indicative maxima in solid brick, not rated specifications; for structural, heavy or safety-critical fixings, step up to an engineered anchor and follow the manufacturer's data.