How to measure a bearing

How to Measure Bearings
Most bearings have their part numbers engraved on the bearings themselves, but these often rub off over time and so it may be necessary to measure the bearing yourself to determine the correct part number.

You can measure the dimensions of a bearing by using a vernier caliper like the one below or measuring accurately with a ruler.
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All bearings will have an inner diameter (ID), an outside diameter (OD) and width (W). Bearings are sometimes referenced by these dimensions, in that order: ID x OD x W.

Measure the ID
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Insert the outer anvils of the caliper (the ones on top of the picture above) into the bore as shown and open the caliper until it isa good fit, but not tight, now read the value on the caliper. In the absence of a caliper a good quality steel ruler will suffice.
Measure the OD
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To measure the outside diameter of a bearing place the jaws of the caliper around the bearing and close it until its a good fit but not tight, now read the value from the caliper.
Measure the Width
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In the same manner as you measured the outside diameter measure the width of the bearing.
Bearing Suffixes - If you are trying to determine the part number of your bearing, you may still need to know the suffix of the part number. Check out our Bearing Suffixes Page to assist you in determining that information.