Drill Bit Sizes in inches and mm – Chart Guide

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Drill bits are available in different materials, lengths, and diameters. Most are measured by the metric units and in the USA it’s imperial units. Drill bit diameter is the most important factor in the drilling process and it should know precisely as much as possible to sharpen or tolerate the diameter.

All over the world, one of the metric or imperial units is used as the general unit. When you use this you have to convert each with different units types.

12 Types Drill Bit for Wood
12 Types Drill Bit for Wood

1 inch is equal to 25.4 mm. By dividing the inches other fractions are introduced. Inches are really popular in the USA but beyond that mostly used the SI units. So we have to interchange the metric units and imperial units.

The below table will introduce you to the fractions and decimals of the inches with mm.

1 inch = 2.54 cm = 25.4 mm

Fractioninchmm
1⁄640.0156250.396875
1⁄320.031250.79375
3⁄640.0468751.190625
1⁄160.06251.5875
5⁄640.0781251.984375
3⁄320.093752.38125
7⁄640.1093752.778125
1⁄80.1253.175
9⁄640.1406253.571875
5⁄320.156253.96875
11⁄640.1718754.365625
3⁄160.18754.7625
13⁄640.2031255.159375
7⁄320.218755.55625
15⁄640.2343755.953125
1⁄40.256.35
17⁄640.2656256.746875
9⁄320.281257.14375
19⁄640.2968757.540625
5⁄160.31257.9375
21⁄640.3281258.334375
11⁄320.343758.73125
23⁄640.3593759.128125
3⁄80.3759.525
25⁄640.3906259.921875
13⁄320.4062510.31875
27⁄640.42187510.715625
7⁄160.437511.1125
29⁄640.45312511.509375
15⁄320.4687511.90625
31⁄640.48437512.303125
33⁄640.51562513.096875
17⁄320.5312513.49375
35⁄640.54687513.890625
9⁄160.562514.2875
37⁄640.57812514.684375
19⁄320.5937515.08125
39⁄640.60937515.478125
5⁄80.62515.875
41⁄640.64062516.271875
21⁄320.6562516.66875
43⁄640.67187517.065625
11⁄160.687517.4625
45⁄640.70312517.859375
23⁄320.7187518.25625
47⁄640.73437518.653125
3⁄40.7519.05
49⁄640.76562519.446875
25⁄320.7812519.84375
51⁄640.79687520.240625
13⁄160.812520.6375
53⁄640.82812521.034375
27⁄320.8437521.43125
55⁄640.85937521.828125
7⁄80.87522.225
57⁄640.89062522.621875
29⁄320.9062523.01875
59⁄640.92187523.415625
15⁄160.937523.8125
61⁄640.95312524.209375
31⁄320.9687524.60625
63⁄640.98437525.003125
1125.4
Drill Bit Sizes in inches and mm table

Remembering everything is not easy. As for me I use this gauge to quickly identfy the drill bit size in inches and milimeters.

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Tom Mackenzy

I am Tom, I am really interested in DIY projects. I have my own workshop and I spend my free time with so many projects. So I would like to share my experience with you regarding power tools, woodworking, metalworking, etc.

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