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How to Measure Gaskets


The Ring Gasket is the possibly the most common shape of gasket. It is also the easiest to measure. Simply measure the diameter of the inside of the circle – also called and inside diameter or I.D. Then, measure the diameter the outside of the circle, also called the outside diameter- or O.D.

Dimensions needed to measure a Ring Gasket:

  • Inside Diameter (I.D.)
  • Outside Diameter (O.D.)


A full face or bolt hole gasket consists of five measurements. First, measure the Inside Dimension (I.D.) and Outside Dimension (O.D.) just like you would a ring gasket. Then, count the number of Bolt holes and also measure the diameter of the bolt holes. The final dimension is the Bolt Circle. The bolt circle is most difficult and confusing dimension to measure and understand for most people. It doesn’t have to be. The Bolt Circle is easily measured from the left side of one bolt hole to the left side of bolt hole across the diameter (bolt hole directly opposite it) or the right side of one bolt hole to the right side of bolt hole across the diameter (bolt hole directly opposite it).

Dimensions needed to measure a Full Face:

  • ID
  • OD
  • Number of Bolt Holes
  • Diameter of the Bolt Holes
  • Bolt Circle


The most common shape for a boiler gasket is an ellipse. Elliptical boiler gaskets are called handway and manway gaskets for small and large gaskets respectively. When measuring an elliptical boiler gasket, you need four dimensions: the two inside diameters, the width and the thickness of the gasket. Usually, standard boiler gasket are made of ¼" rubber. The first inside dimension consists of the length from top to bottom of the inside of the gasket. The second inside dimension is the length from right to left on the inside of the gasket. There are other shapes for boiler gasket such as an oblong, a pear, or a round shape. If you have any questions on how to measure a particular gasket just ask a member of Hennig Gasket staff. Also, please feel free to stop in with a sample of the old gasket or send Hennig Gasket sample through the mail.

Dimensions needed for an Elliptical Boiler Gasket:

  • First Inside Diameter (top to bottom)
  • Second Inside Diameter (left to right)
  • Width of Cross Section
  • Thickness of Material

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