This is the most comprehensive wall plug size chart available for UK DIYers and tradespeople. It covers every standard wall plug colour, the exact drill bit size you need, the correct screw gauge and length, and the approximate load capacity in solid masonry.
Bookmark this page — you’ll come back to it every time you pick up a drill.
Wall Plug Size Chart — Complete UK Reference
| Plug Colour | Plug Diameter | Drill Bit Size | Screw Gauge (No.) | Screw Diameter (mm) | Recommended Screw Length | Load in Brick (approx.) |
|---|---|---|---|---|---|---|
| Yellow | 5mm | 5mm | No. 4–8 | 3.0–4.0mm | 25–40mm | 5–10 kg per fixing |
| Red | 6mm | 6mm | No. 6–10 | 3.5–5.0mm | 30–50mm | 15–25 kg per fixing |
| Brown | 7mm | 7mm | No. 8–14 | 4.0–5.5mm | 40–70mm | 20–35 kg per fixing |
| Blue | 10mm | 10mm | No. 14–18 | 6.0–8.0mm | 60–100mm | 40–75 kg per fixing |
Important notes:
- Load ratings are approximate and assume solid brick or dense concrete block. Lightweight blocks, thermalite, and aircrete have significantly lower holding power.
- Always use at least two fixings for any wall-mounted item. Load ratings above are per individual fixing.
- The screw should be long enough to pass through the item being fixed, through the wall plug, and at least 5mm into the masonry behind.
How the Sizing System Works
The UK wall plug system is beautifully simple once you understand the logic: the plug diameter equals the drill bit diameter. A 6mm red plug goes into a 6mm hole drilled with a 6mm masonry bit. The screw then goes inside the plug and expands it against the sides of the hole, creating a friction grip in the masonry.
The screw gauge determines how much the plug expands. Too thin a screw and the plug won’t grip properly. Too thick and you’ll split the plug or struggle to drive the screw home. The chart above gives the correct gauge range for each plug size.
Screw Gauge to Millimetre Conversion
UK screws are sold in both gauge numbers and metric sizes, which causes endless confusion. Here’s the conversion table:
| Screw Gauge (No.) | Diameter (mm) | Common Uses |
|---|---|---|
| No. 4 | 2.9mm | Small hinges, light brackets, cable clips |
| No. 6 | 3.5mm | Light shelving, small hooks, switch plates |
| No. 8 | 4.0mm | General purpose — shelves, curtain poles, most brackets |
| No. 10 | 5.0mm | Heavier brackets, TV mounts, handrails |
| No. 12 | 5.5mm | Heavy-duty brackets, gate hinges |
| No. 14 | 6.0mm | Coach screw applications, structural brackets |
Choosing the Right Screw Length
The screw must be long enough to pass through three things:
- The item being fixed — the bracket, shelf support, or mounting plate
- The full length of the wall plug — so the screw engages the entire plug
- At least 5mm extra — to ensure the screw tip reaches the back of the plug and fully expands it
For example, if you’re mounting a bracket that’s 3mm thick using a 30mm red wall plug, you need a screw at least 38mm long (3mm bracket + 30mm plug + 5mm extra). In practice, a 40mm screw would be the right choice.
Drill Bit Types — Which Bit for Which Wall?
| Wall Material | Drill Bit Type | Drill Setting | Notes |
|---|---|---|---|
| Solid brick | Masonry bit (TCT tip) | Hammer drill mode | Standard approach — use hammer action for best results |
| Concrete / dense block | Masonry bit (TCT tip) | Hammer drill mode | May need SDS drill for reinforced concrete |
| Lightweight block (thermalite) | Masonry bit (TCT tip) | Drill mode only (no hammer) | Hammer action can crumble the block — drill gently |
| Plasterboard | HSS or wood bit | Drill mode only | Standard wall plugs don’t work — use specialist fixings |
| Tile (over masonry) | Tile/glass bit, then masonry bit | Drill mode through tile, then hammer | Start with tile bit to prevent cracking, switch to masonry once through |
| Timber / stud | HSS or wood bit | Drill mode | No wall plug needed — screw directly into timber |
A good masonry drill bit set covering 5mm, 6mm, 7mm, 8mm, and 10mm will handle virtually any wall plug job. Check price on Amazon
When to Use Each Plug Size
Yellow Plugs (5mm) — Light Duty
Yellow plugs are for light loads only. Think picture hooks (for lightweight frames), cable clips, small decorative brackets, and thermostats. If the item weighs more than about 5 kg total (spread across all fixings), step up to red plugs.
Common mistake: Using yellow plugs for smoke detectors or carbon monoxide alarms on ceilings. Ceiling fixings are under constant gravitational pull — use red plugs for anything mounted overhead.
Red Plugs (6mm) — General Purpose
Red plugs are the UK’s workhorse fixing. They handle the majority of household tasks: curtain pole brackets, towel rails, bathroom accessories, shelving brackets (for lightly loaded shelves), coat hooks, and light-to-medium wall-mounted cabinets.
A pair of red plugs in solid brick, with No. 8 × 50mm screws, will comfortably hold a loaded coat rack or a bathroom mirror. Fischer red plug assortment — check price on Amazon
Brown Plugs (7mm) — Heavy Duty
When the job is structural or the load is significant, brown plugs are your go-to. TV wall mounts, heavy floating shelves, boiler flue brackets, garden trellis battens, wall-mounted towel radiators, and kitchen wall cabinets all call for brown plugs.
For a TV mount holding a 25 kg television, four brown plugs in solid brick give a combined holding capacity well in excess of 80 kg — providing a very comfortable safety margin. Fischer brown plug box — check price on Amazon
Blue Plugs (10mm) — Extra Heavy Duty
Blue plugs are for the heaviest domestic fixings: large TV brackets for 55–75 inch screens, security gates, external handrails, heavy-duty shelving systems, and structural supports. In commercial settings, they’re used for signage, equipment mounts, and heavy racking.
Blue plugs require a 10mm hole, which means a decent hammer drill or SDS rotary hammer. A standard cordless combi drill can manage 10mm in brick but will struggle in dense concrete.
Pro Tips for Perfect Fixings Every Time
- Mark the drill depth: Wrap a piece of masking tape around the drill bit at the correct depth so you don’t drill too deep or too shallow.
- Vacuum the hole: Dust left in the drilled hole reduces the plug’s grip. A quick blast with a vacuum nozzle makes a real difference.
- The plug should be a firm push fit: If it slides in loosely, the hole is oversized — try the next plug size up, or use a chemical anchor.
- Don’t over-tighten: Once the screw is snug and the bracket doesn’t move, stop. Over-tightening can spin the plug in the hole and destroy its grip.
- Avoid drilling near edges: Keep at least 50mm from the edge of a brick to avoid cracking it. Never drill into mortar joints — they have far less holding power than the brick itself.
- Use a detector first: Always scan for pipes and cables before drilling, especially in kitchens, bathrooms, and above/below sockets and switches. Stud & pipe detector — check price on Amazon
Frequently Asked Questions
What size drill bit for a red wall plug?
A red wall plug requires a 6mm masonry drill bit. The drill bit size always matches the plug diameter — red plugs are 6mm, so you need a 6mm bit. Pair with a No. 8 × 40mm or No. 10 × 50mm screw for most household applications.
What size drill bit for a brown wall plug?
A brown wall plug requires a 7mm masonry drill bit. Use with a No. 10 × 50mm or No. 12 × 60mm screw depending on the bracket thickness and load. Brown plugs are the go-to choice for heavy fixings like TV mounts and heavy shelving.
What’s the difference between a No. 8 screw and a 4mm screw?
A No. 8 gauge screw has a shank diameter of approximately 4.0mm, so they’re essentially the same thing. The UK gauge system (No. 4, 6, 8, 10, etc.) is gradually being replaced by metric measurements, but you’ll still see both on packaging. See our conversion table above.
Can I use a bigger plug if the hole is too large?
Yes — if you’ve accidentally drilled too wide, step up to the next plug size. A 7mm brown plug in an oversized 6mm hole works well. For significantly oversized holes, consider using a chemical anchor (resin fixing) which fills the gap and bonds to the masonry.
What if I hit a hard spot while drilling brick?
You’ve likely hit the engineering brick or a piece of flint/aggregate in the concrete. Keep the hammer drill on, apply steady pressure, and let the bit do the work. Don’t force it — this overheats the bit and dulls the cutting edge. If the bit isn’t making progress, try a fresh sharp masonry bit.
Related Guides
- Wall Plug & Fixing Compatibility Guide — Main Hub
- Masonry Wall Plugs & Fixings Guide
- Plasterboard Fixings Guide
- Cavity Wall Fixings Guide
- What Fixings for a TV Mount?
- What Fixings for Curtain Poles?
- What Fixings for Heavy Shelves?
- What Fixings for Heavy Mirrors?
Recommended Wall Plug Kits
Having the right selection of plugs and matching drill bits saves multiple trips to the hardware shop. These kits cover the most common sizes.
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Check Price on Amazon
