Identification
How to Measure a Stamp's Perforations
A stamp's perforation is measured as the number of perforation holes in a length of two centimetres, using a perforation gauge. It matters because the same stamp design can exist with different perforations, which can make it a different, and differently valued, stamp. To measure it, lay the stamp on a perforation gauge and slide it until the holes line up exactly with one of the gauge's rows; the number beside that row is the perforation.
At a glance
What perforation measurement means
When stamps are perforated, the rows of holes are made to a particular spacing, and that spacing is described by a number: how many holes fall within two centimetres. A "perforation 14" stamp has fourteen holes in that length, a "perforation 11" stamp has eleven, and so on.
It sounds technical, but it is simply a way of recording how fine or coarse the perforations are. Our glossary entry on perforation gives the background, and it matters because the same design can appear with different perforations from different printings.
How to measure perforations, step by step
Place the stamp on the gauge.
A perforation gauge is a card or metal scale printed with rows of dots at different spacings, each labelled with a number.
Slide the stamp along the rows.
Move it up or down until the perforation holes line up exactly over the dots of one row.
Read the number.
The figure printed beside the matching row is the perforation, for example 14 or 11.
Measure each side.
The horizontal and vertical perforations can differ, so measure both. A stamp measuring 14 across and 15 down is described as perf 14 x 15.
Note compound perforations.
Where the sides differ, both numbers form part of the stamp's identity.
Why perforation matters for value
A small difference, a different stamp
Perforation is one of the features that decides a stamp's exact identity, and two stamps that look identical can be quite different, and differently valued, because of it. With the watermark, it often determines which catalogue number a stamp carries. Our guides to identifying a watermark and identifying a stamp set out the wider method, and reading an SG number explains how the catalogue records these differences.
Frequently asked questions
Lay the stamp on a perforation gauge and slide it until the holes line up exactly with one of the gauge's rows. The number beside that row is the perforation. Measure each side, as they can differ.
It means there are fourteen perforation holes in a length of two centimetres along that edge. The number describes how fine or coarse the perforations are.
Because the same stamp design can exist with different perforations from different printings, which can make it a different stamp with a different value.
A stamp whose horizontal and vertical perforations differ, for example 14 across and 15 down, described as perf 14 x 15. Both numbers form part of its identity.
Founder and stamp dealerLast updated June 2026