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”