Drill Size Chart

A drill size chart shows the correct drill bit sizes for pilot holes, clearance holes and fixings, with conversions between metric, decimal inch and fractional sizes.

Drill size chart showing common metric, decimal inch and nearest fractional inch drill sizes, with guidance for pilot holes, clearance holes, wood screws, masonry fixings and general metal fabrication work.

This reference is useful for engineers, fabricators, tradespeople, installers and DIY users who need to choose the correct drill bit size for accurate hole sizing and reliable fixing performance.

How to Use This Drill Size Chart

Choosing the correct drill size depends on the material being drilled, the fixing being used and whether the hole is for clearance, piloting or tapping.

• Pilot holes – guide screws into timber and reduce the risk of splitting
• Clearance holes – allow screws or bolts to pass freely through the material
• Tapping holes – used when cutting threads into metal
• Masonry drill sizes – matched to wall plugs and fixing systems

Using the correct drill size improves accuracy, reduces material damage and helps create stronger, cleaner fixings.

For example, a 5mm drill bit is approximately 13/64″, making it a common size for wall plugs and general fixing work.

Common Drill Size Chart

The table below shows commonly used drill sizes with metric, decimal inch and nearest fractional equivalents, along with typical applications.

Note: Fractional sizes shown are the nearest commonly available imperial drill sizes and may not be exact equivalents.

Pilot Hole Sizes for Wood Screws

Pilot holes are especially important when drilling timber, as they help guide the screw and reduce the risk of splitting. Hardwood typically requires a slightly larger pilot hole than softwood due to increased density and resistance.

For a full reference including screw gauges, pilot holes, clearance drill sizes, wall plug colours and masonry drill sizes, see our wood screw gauge chart.

Clearance Hole Sizes

A clearance hole allows a screw, bolt or fixing to pass through one piece of material without the thread engaging. This helps pull materials tightly together during assembly.

As a general rule, clearance holes should be slightly larger than the outside diameter of the screw or bolt being used.

Drill Sizes for Metal Fabrication

When drilling metal, accurate hole sizing is important for fixings, assembly, folding, fabrication and installation. Metals such as aluminium, stainless steel, brass, copper and mild steel require suitable drill bits, controlled speed and correct hole sizing to avoid distortion, burrs or poor fit.

This includes applications in sheet metal fabrication, component manufacture and architectural metalwork where accurate hole sizing is critical.

For material thickness reference, see our sheet metal gauge chart, which shows sheet metal thickness conversions between gauge, millimetres and inches.

For precision-cut holes, profiles and repeated parts in sheet metal, our dedicated trade division MS Laser Services provides specialist precision sheet metal laser cutting for thin-gauge materials.

Related Drill and Gauge Resources

This drill size chart forms part of our technical reference section, alongside related guides for screw sizing, sheet metal thickness and fabrication measurements.

• Wood Screw Gauge Chart
• Sheet Metal Gauge Chart

Metal Sheets Ltd supplies a wide range of sheet metals including aluminium, brass, copper, stainless steel, Corten steel and zinc for fabrication, interiors, signage and design applications.

For smaller cut-to-size pieces and part sheets, visit our Metal Offcuts store. For bespoke fabrication or project enquiries, please contact Metal Sheets Ltd.

In this image: Vernier caliper measuring drill diameter for accurate hole sizing.