UK Screw Sizes & Measurements Explained

  • Find out what size screws you need with no effort.
  • Follow our guide on screw sizes and gauges.
UK screw sizes

Take the mystery out of your next DIY endeavour with our handy guide on the UK’s numerous screw sizes.

UK screw sizes

While the metric system uses millimetres to measure screw sizes, the imperial system uses inches. In the UK, we use the metric system (which is prevalent in all of Europe), while the imperial system is used in the US.

For something like a screw, the measurements match up quite nicely when you convert them. However, if you’re trying to figure out liquid measurements, you should know that the US uses different measurements for their pints and gallons.

Despite being a metric area, there are many places in the UK that still use imperial measurements. As such, it’s a good idea to be familiar with both measurements for screws.

In the next few sections, we’ll list each screw by diameter/gauge, and the available sizes for each of those screws.

3mm/Gauge Size 4

For screws that have a diameter of 3mm or are listed as Gauge Size 4:

40mm – 1 ½ inches or 1.5 inches

30mm – 1 ¼ inches or 1.25 inches

25mm – 1 inch

20mm – ¾ inches or 0.75 inches

16mm – 5/8 of an inch or 0.625 inches

12mm – ½ an inch or 0.5 inches

UK screw sizes
Different sizes of screw being drilled into a plank of wood.

3.5mm/Gauge Size 6

For screws that have a diameter of 3.5mm or are listed as Gauge Size 6:

40mm – 1 ½ inches or 1.5 inches

30mm – 1 ¼ inches or 1.25 inches

25mm – 1 inch

20mm – ¾ inches or 0.75 inches

16mm – 5/8 of an inch or 0.625 inches

12mm – ½ an inch or 0.5 inches

4mm/Gauge Size 8

For screws that have a 4mm diameter or are listed as Gauge Size 8:

70mm – 2 ¾ inches or 2.75 inches

60mm – 2 ½ inches or 2.5 inches

50mm – 2 inches

45mm – 1 ¾ inches or 1.75 inches

40mm – 1 ½ inches or 1.5 inches

35mm – 1 3/8 inches or 1.375 inches

30mm – 1 ¼ inches or 1.25 inches

25mm – 1 inch

20mm – ¾ of an inch or 0.75 inches

16mm – 5/8 of an inch or 0.625 inches

12mm – ½ an inch or 0.5 inches

4.5mm/Gauge Size 9

For screws that have a 4.5mm diameter or are listed as Gauge Size 9:

75mm – 3 inches

70mm – 2 ¾ inches or 2.75 inches

60mm – 2 3/8 inches or 2.375 inches

50mm – 2 inches

45mm – 1 ¾ inches or 1.75 inches

40mm – 1 ½ inches or 1.5 inches

35mm – 1 3/8 inches or 1.375 inches

30mm – 1 ¼ inches or 1.25 inches

25mm – 1 inch

5mm/Gauge Size 10

For screws that have a 5mm diameter or are listed as Gauge Size 10:

100mm – 4 inches

90mm – 3 ½ inches or 3.5 inches

80mm – 3 ¼ inches or 3.25 inches

See Also

75mm – 3 inches

70mm – 2 ¾ inches or 2.75 inches

60mm – 2 3/8 inches or 2.375 inches

50mm – 2 inches

45mm – 1 ¾ inches or 1.75 inches

40mm – 1 ½ inches or 1.5 inches

35mm – 1 3/8 inches or 1.375 inches

30mm – 1 ¼ inches or 1.25 inches

25mm – 1 inch

6mm/Gauge Size 12

For screws that have a 6mm diameter or are listed as Gauge Size 12:

110mm – 4 3/8 inches or 4.375 inches

100 – 4 inches

90mm – 3 ½ inches or 3.5 inches

80mm – 3 ¼ inches or 3.25 inches

75mm – 3 inches

60mm – 2 3/8 inches or 2.375 inches

50mm – 2 inches

40mm – 1 ½ inches or 1.5 inches

30mm – 1 ¼ inches or 1.25 inches

UK screw measurements

Specialised wood screws, only to be used on wood.

Troubleshooting your screws

You won’t always know what size screw you need, so instead of using trial and error on the product that you’re putting together, test out a few different sizes of screws on spare wood, brick, and plasterboard if you have any lying around.

Longer screws will, obviously, go further into your walls than shorter screws. But that doesn’t mean using the longest screw is the best choice. You might end up drilling through your plasterboard…

Don’t use wood screws for metal, and it’s better to use wood screws for wood than use a sheet metal screw just because you have it on-hand. There’s a difference between screws that are used outdoor and those used indoor. Look for the “exterior use” note to make sure you’re using the right screws. Exterior screws are hardier than indoor screws.

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