I Have a tool for measuring the sizes of holes and screws but I don’t know what size is listed as 10 in the image below. Across from it the row in question is listed as INCH.

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A #10 screw will be a close fit in the 10 hole and is approximately 3/16" in diameter. The tolerance on a #10 screw ranges from about 0.182" to 0.190". Gauges of this kind are not intended to make precise measurements, but to easily identify fasteners.


If you are speaking of the holes marked 4,5,6,8,10, these are small bolt sizes. There is 1 size missing and that is #12. Most sizes with diameters less than 3/16" are listed as number sizes. I hope this helps and is what you are asking about.

  • As @d george stated, diameter size smaller than 3/16" are designated by a one or two digit numbers as shown on your gauge. Do not expect these number to translate to a nice clean factions. Only #5 matches up to 1/8", In a hardware store, you will see the small bolts and screws organized by size 6, 8, 10 and 12 as the most common sizes. – Programmer66 Apr 12 at 1:50

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