📏 Perforation Gauge Reference Chart
A general reference for how stamp perforation ('perf') measurements work and commonly seen values, measured as the number of perforation holes per 2 centimeters of edge.
What a perforation gauge measures
A perforation gauge counts holes, not teeth, along a fixed 2 centimetre span of the stamp's edge. That count is the gauge number:
perf number = holes counted per 20 mm of edge
hole pitch = 20 mm / perf number
perf 14 -> 20 / 14 = 1.43 mm between hole centres
perf 11 -> 20 / 11 = 1.82 mm between hole centresA higher number means finer, more closely spaced holes, not bigger ones. On a printed gauge, slide the stamp until the dots line up with every hole in the run; a line that fits three holes and misses the fourth is the wrong one. Quarter-gauge steps (11, 11¼, 11½, 11¾) are catalogued as separate varieties, so read to the quarter.
Compound perfs, and what the gauge cannot tell you
When the two axes differ, catalogues quote the horizontal edges first: perf 11 x 10½ means top and bottom gauge 11, the sides 10½. Measure all four edges before calling a stamp uniformly perforated.
- It cannot authenticate a stamp. A reperforated copy with trimmed margins can gauge exactly right, and often does - that is the point of the fake.
- It cannot tell comb from line perforation. That is judged from the corner holes and row alignment, not from the number.
- It says nothing about watermark, paper or printing method. Those are separate tests, and a perf variety usually needs one of them too.
Frequently asked questions
What does perf 11 x 10.5 mean?
Eleven holes per 2 cm along the top and bottom edges, and ten and a half per 2 cm along the sides. A stamp perforated the same on all four edges is written as one number.
How do I measure perforations without a gauge?
Lay a millimetre ruler along one edge and count the holes falling within 20 mm. It works, but the answer rounds to whole gauges; quarter-gauge varieties need a proper gauge.
Does the perforation prove which variety I have?
Only alongside the rest. Perf separates issues that are otherwise identical, but catalogues normally also specify watermark, paper and colour before a listing is settled.