Stamp perforations are the row of small holes punched between stamps so they tear apart cleanly, but the exact number of those holes per two centimeters, called the gauge, is one of the most overlooked ways to tell an ordinary stamp from a rare one. To measure it, line the stamp's edge up against a perforation gauge and read the number where the teeth match the gauge's marks exactly. Two stamps that look identical can carry different gauges because of a printing plate change, a different print run, or a genuine variety, and that difference can be the entire reason one is worth ten cents and the other is worth a few hundred dollars.
What Do the Numbers on a Perforation Gauge Actually Mean?
A perforation gauge measures how many holes (or "teeth") appear across two centimeters of a stamp's edge. A stamp described as "perf 11" has 11 holes per two centimeters along that edge; "perf 12" has 12, and so on. The number has nothing to do with how many stamps were on a sheet. It is purely a measurement of how tightly or loosely the perforating machine punched the paper.
This matters because postal printers changed perforating equipment often, sometimes mid-print-run, and different countries and eras standardized on different gauges. A slight shift, such as perf 10 versus perf 11 on an otherwise identical design, can mark a completely different printing, and pricing in stamp catalogs (Scott, Michel, Stanley Gibbons) is frequently split by gauge alone.
How to Measure Stamp Perforations in 3 Steps
What you'll need: a perforation gauge (plastic, metal, or electronic), a flat well-lit surface, and stamp tongs so you don't handle the stamp with bare fingers.
- Lay the stamp flat and lift it only with tongs. Oils from your fingers can discolor paper over time, and bare-finger handling is one of the fastest ways to devalue an otherwise mint stamp.
- Line up one edge of the stamp against the gauge's printed scale. Most gauges print a series of graduated dot or line patterns, each labeled with a number. Slide the stamp along the scale rather than guessing by eye.
- Read the number where the perforation teeth align exactly with the gauge's dots. A close match isn't good enough. If the teeth fall slightly ahead of or behind every dot in a row, move to the next line on the gauge. Many stamps need to be checked on more than one edge, since some issues are deliberately compound (see below).
Doubles as a close-up viewer and a scale for checking perforation alignment by eye before you gauge it.
Can a Stamp Have Two Different Perforation Numbers?
Yes, and this is where a lot of collectors get tripped up. Compound perforations occur when a stamp is gauged differently on its horizontal and vertical edges, for example perf 11 across the top and bottom but perf 12 down the sides. Catalogs list these as two numbers separated by a small "x", such as "11 x 12". Always check all four edges before recording a stamp's gauge, since checking only one side can lead you to misidentify a variety entirely. Once you've confirmed a variety, it's worth logging it properly. Our guide on how to organize a stamp collection covers how collectors typically track varieties like these by country, era, or catalog number.
Common Perforation Gauges and What They Signal
| Gauge | Typically seen on | Why it matters to collectors |
|---|---|---|
| Perf 10 | Early-to-mid 20th century US issues | Coarser perforation, wider teeth; common on many workhorse definitives |
| Perf 11 | Most 20th century US and European issues | The most widely used gauge; the "default" collectors compare everything else against |
| Perf 12 | Earlier classic-era issues | Finer teeth; a shift from 11 to 12 on the same design often marks a distinct printing |
| Perf 13 to 14 | Commemoratives, later coil issues | Finer gauges used where cleaner separation was needed for smaller sheet formats |
| Perf 15 and finer | Rare specialty and early 20th century issues | Uncommon; worth a second look and a catalog check every time |
For a full technical breakdown of gauge scales and how they were standardized, the Wikipedia entry on perforation gauges is a solid reference alongside your Scott or Michel catalog.
Why Perforation Errors Can Turn an Ordinary Stamp Into a Rare One
Perforation mistakes happen at the printing press, and collectors chase them precisely because they're accidents that were never supposed to leave the building. The most valuable categories:
- Imperforate stamps, missing their perforations entirely, usually from a sheet that skipped the perforating machine. Genuine imperforate errors from modern issues can be worth many multiples of the perforated version.
- Shifted or misregistered perforations, where the perforating pattern is punched off-center, cutting into the design itself rather than the margin.
- Double perforations, where the sheet passed through the perforating machine twice at a slightly different position, leaving two overlapping rows of holes.
A word of caution: not every imperforate-looking stamp is a genuine error. Some have been deliberately trimmed and "reperforated" to imitate a rarer variety or to disguise damage, and this kind of alteration can be difficult to catch by eye. An electronic gauge that reads perforation spacing to a fraction of a millimeter, rather than relying on your eye against a printed scale, is the more reliable way to confirm a stamp's perforation is original and consistent all the way around before you buy or sell based on it.
Reads perforation gauge digitally in seconds, removing the guesswork of matching teeth to a printed scale by eye, and helps catch reperforated or altered stamps.
Tongs for safe handling, a lighted magnifier for close inspection, and a measuring tape, in one travel case.
Frequently Asked Questions
What is a stamp perforation gauge?
A perforation gauge is a printed or digital tool used to count how many perforation holes appear across two centimeters of a stamp's edge, letting collectors identify and compare stamp varieties that otherwise look identical.
What does "perf 11" mean on a stamp?
It means the stamp has 11 perforation holes per two centimeters along the measured edge. It's a physical measurement of the perforating machine's spacing, not a rarity rating on its own, though certain gauges on certain issues are much scarcer than others.
Can one stamp have two different perforation measurements?
Yes. These are called compound perforations, and they happen when the horizontal and vertical edges were punched at different gauges, commonly written as two numbers such as "11 x 12".
Are imperforate stamps always more valuable?
Genuine imperforate errors, where a sheet skipped perforation during production, are usually worth significantly more than the standard issue. Trimmed or reperforated stamps made to look imperforate are not, which is why confirming authenticity with a precise gauge matters before buying.
How can I tell if a stamp's perforations have been altered or faked?
Look for teeth that are unevenly spaced, slightly rounded rather than crisp, or inconsistent when measured on all four sides. An electronic gauge that measures to a fraction of a millimeter catches inconsistencies a printed gauge or the naked eye can miss.
Do I need an electronic gauge, or is a plastic one accurate enough?
For everyday sorting and cataloging, a plastic or metal gauge is accurate enough. For higher-value stamps, authentication, or catching reperforation, an electronic gauge like the PERFOtronic gives a more precise and repeatable reading.
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