Wall Plug Drill Size Chart: Yellow, Red, Brown, Blue — and Why Plugs Spin

Every fitter knows the colours; the failures come from everything around them. A wall plug that spins, a screw that never tightens, a bracket that pulls out with a cone of dust — none of those are the plug’s fault. They are a drill bit half a millimetre oversize, a hole drilled to the wrong depth, or hammer mode used on a wall that cannot take it. The chart first, then the three rules that make it hold.

The colour chart

The drill size is the plug size — a 6 mm plug wants exactly a 6 mm hole in masonry. There is no "drill a bit small so it grips" in brick or concrete; an undersized hole shears the plug’s fins off as it is hammered in, and the grip you feel is fins packed as debris.

Depth and screw length — the two numbers nobody measures

• Hole depth = plug length + 10 mm. The spare depth swallows the dust you cannot blow out and lets the plug sit flush or just below the surface. A plug proud of the wall levers the fixture off it.
• Screw length = plug length + fixture thickness + one screw diameter. The screw tip must pass right through the plug’s end, because the tip is what spreads the far end into the masonry. A short screw expands only the mouth — strong enough to feel tight, weak enough to fail later.
• Blow the hole out (dust blower or a squeeze bottle, glasses on). Dust lining the hole acts as a release agent between plug and masonry.

And keep the screw inside the plug’s printed range. A bigger screw does not mean more grip: oversized, it bursts the plug before the fins ever load the masonry, and near an edge it cracks the brick. Undersized, it never spreads the fins at all — the fixing holds on friction and fails on the first real load. The range moulded into the bag is engineering, not a suggestion.

Match the drilling mode to the wall

The full drilling technique for the first row — SDS mechanism, feed pressure, dust — is covered in drilling into concrete. The short version: let the hammer do the work, keep the bit straight, and never lean on it to "help".

From our range

Carbide Tip Multipurpose Drill Bit 1/4 Inch Quick Change Hex Shank Masonry Drill Bit

Carbide multi-purpose bit on a ¼" hex shank — tile face, render and brick with one bit in a cordless driver.

From our range

SDS Plus Hammer Drill Bit Cross Tip Carbide Masonry Drill Bit with Single/Double Flute Sandblasting Impact Bit

SDS-Plus cross-tip bits hold their diameter over hundreds of plug holes — the cure for spinning plugs on site.

Placement details that decide the load

• Fix into the brick, not the mortar joint, for anything heavier than a picture. Mortar crumbles around the plug under load.
• Keep 60 mm from brick edges — expansion force cracks out a corner closer than that.
• In old soft brick, step down a duty class: a brown plug’s expansion can burst a century-old brick. Two red fixings beat one brown one.
• For repeated fixing points (racking, machinery), plugs are the wrong tool — through-bolts or resin anchors carry vibration; plugs work loose.

For the counter and the container

Plug holes are drilled in millions daily, which makes the 5, 6, 7 and 10 mm masonry and SDS-Plus bits the fastest-wearing, fastest-reselling drill sizes in any hardware shop. They outsell every other masonry diameter combined, and a counter that runs out of 6 mm on a Saturday loses the plug sale, the screw sale and the bracket sale with it. We ship these four sizes in bulk boxes precisely because the reorder pattern is that predictable.

Full version with every size: the drill size converter.