How to Read Perforations on Postage Stamps

Written by patti perry
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How to Read Perforations on Postage Stamps
Beginning stamp collectors should learn how to use a perforation guage. (stamp image by hugy from

Postage stamp perforations are read with a gauge made of paper, cardboard, plastic or metal. Gauges may be of a dot variety or the line type. The "count" or "gauge" of a stamp is always a standard equal to the number of holes in 20mm. The gauge determines the value of a stamp and designates its authenticity. Since the mid-20th century, most U.S. stamps are printed with the standard "Perf." of 11 inches by 10.5 inches. These numbers refer to the horizontal measurement first and then the right vertical side.

Skill level:
Moderately Easy

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Things you need

  • Perforation gauge

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    Dot Perforation Gauge

  1. 1

    Lay a stamp across the little black spot on the dot perforation gauge.

  2. 2

    Move the stamp up and down on one side until all the holes in the stamp are filled by the black dots on the gauge.

  3. 3

    Read the numbers off the side of the gauge to determine the perforation count.

    Line Perforation Gauge

  1. 1

    Place your stamp onto the line gauge, which is a more accurate type of gauge.

  2. 2

    Line up the vertical left line of your stamp by placing the middle of the farthest left perforation line over the left line on the gauge.

  3. 3

    Move the gauge up and down so all the lines are in the centre of the stamp's perforation holes.

  4. 4

    Check the line and hole in the centre last.

  5. 5

    Read the value from either side of the gauge, when all the lines and holes line up.

Tips and warnings

  • Some stamps have different perforations on each side.
  • Plastic perforation gauges may shrink after 10 years. Verify that old gauges are still accurate in their count by comparing its readings to another gauge of that same type.

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