How to Measure Taper Pins

16th June 2026

Step 1: Measure the large end diameter
Use calipers to measure the widest end of the taper pin.

Step 2: Measure the overall length
Measure from end to end.

Step 3: Match the diameter to the chart
Use the large end diameter to find the correct taper pin number.

Step 1: Measure the smaller end diameter
Use calipers to measure the narrowest end of the taper pin.

Step 2: Measure the length
Measure from end to end.

Step 3: Finding the pin
Use the small end diameter with the length to find the correct size.

Example: Measuring a #2 x 1″ Taper Pin

Measure the large end diameter

Measure the overall length

Large end diameter: 0.193″, or approx. 3/16″

Length: 1″

Correct size: #2 x 1″

Use the large end diameter to match the taper pin to the correct pin number.

Pin No.	Large End Diameter	Approx. Fraction	Approx. Metric Equivalent
#0	0.156"	5/32”	3.93 mm
#1	0.172"	11/64”	4.36 mm
#2	0.193"	3/16”	4.76 mm
#3	0.219"	7/32”	5.55 mm
#4	.250"	1/4”	6.35 mm
#5	0.289"	19/64”	7.54 mm
#6	0.341"	11/32”	8.7 mm
#7	0.409"	13/32”	10.3 mm
#8	0.492"	1/2”	12.7 mm
#9	0.591"	19/32”	15.0 mm
#10	0.706"	23/32”	18.2 mm

Imperial taper pins use a 1:48 taper. This means the diameter changes by 0.0208″ for every 1″ of length.

Small end diameter = large end diameter – (length ÷ 48)

0.193″ – (1″ ÷ 48) = 0.1722″

So the small end diameter is approximately 0.172″.

Metric taper pins use a 1:50 taper. This means the diameter changes by 1 mm for every 50 mm of length.

Large end diameter = small end diameter + (length ÷ 50)

100 mm – (100 mm / ÷ 50) = 0.98 mm

So the small end diameter is approximately 0.98 mm

Select a part number below to view product details. Scroll sideways to view all available lengths.