Gauge Fit Guide

It can be confusing when some gauges are offered with millimeter(mm) sizes and other with inch sizes.  Here’s how to navigate between them.  

How to use:  Column A is the measured millimeter size.  Column C is the nearest inch size.  

If you usually wear 18mm gauges, what would this be in inches? 

Look down Column A for your usual millimeter size.  Slide right along that row to see the nearest inch size in Column C: 11/16.

Then look in Column E to find out that the difference between the millimeter size and the inch size is .02”, 2 hundredths of a inch, such a small difference that both sizes will fit you.

(Columns B and D contain the mm and inch measurements converted to hundredths of an inch)

A = Millimeters sizes (measured by electronic calipers)

B = Millimeters converted to hundredths of a inch

C = Nearest size in inches

D = Inches converted to hundredths of an inch

E = Difference between mm size and inch size

A	B	C	D	E
10mm	.34”	3/8	.38”	.04”
12mm	.47”	1/2	.50”	.03”
14 mm	.55”	9/16	.56”	.01”
16 mm	.63”	5/8	.63”	.00”
18 mm	.71”	11/16	.69”	.02”
20 mm	.79”	13/16	.81”	.02”
22 mm	.87”	7/8	.86”	.01”
24 mm	.95”	15/16	.94”	.01”