Stamp Perforations Guide: Measuring, Types & How They Affect Value

Perforations are the small holes punched between stamps that allow them to be easily separated from a sheet. While they might seem like a simple practical feature, perforations are one of the most important elements in stamp identification and can dramatically affect a stamp's value. A difference of just half a perforation measurement can mean the difference between a common stamp and a rare variety worth hundreds of times more.

This guide covers everything you need to know about stamp perforations: their history, how to measure them, the different types, and why perforation varieties matter so much to collectors and dealers.

A Brief History of Stamp Perforations

The world's first postage stamps, including the famous Penny Black of 1840, were issued without perforations. Sheets of stamps had to be cut apart with scissors or a knife, which was slow, imprecise, and often resulted in damaged stamps. Post office clerks and the public alike found this process frustrating.

The solution came from Henry Archer, an Irish businessman and inventor who developed the first practical perforating machine in 1848. After years of experimentation and trials, the British Post Office officially adopted perforations in 1854, and the first perforated stamps were the Penny Red stars. Within a decade, nearly every major postal authority worldwide had adopted some form of perforation. It was one of the most significant practical innovations in postal history.

"Henry Archer's perforating machine transformed stamp production and created an entirely new dimension of philatelic study. Every perforation variety tells a story about the machinery, the era, and the postal system that produced it."

How to Measure Perforations

Perforation measurement counts the number of perforation holes (or teeth) that fit within a span of 2 centimeters along the edge of a stamp. This measurement is taken using a perforation gauge, one of the essential tools for any stamp collector.

Using a Perforation Gauge

1. Place your stamp on the gauge: Position the stamp so that one edge aligns with the rows of dots printed on the gauge
2. Slide until aligned: Move the stamp up or down until the perforation teeth match perfectly with a row of dots on the gauge
3. Read the number: The number printed next to the matching row is your perforation measurement
4. Measure all sides: Check both horizontal and vertical edges, as they may differ

Perforation gauges are available in several formats: printed card gauges (the most affordable option), metal gauges (more durable and precise), and digital/electronic gauges for advanced collectors. A basic printed gauge costs just a few dollars and is perfectly adequate for most collectors.

Perforation Types

The method used to perforate stamps affects their appearance, particularly at the corners. Understanding these types helps with both identification and authentication.

Line Perforation

The simplest and earliest method, line perforation punches one straight line of holes at a time across the entire sheet. The sheet is first perforated in one direction (all horizontal lines), then turned 90 degrees and perforated again (all vertical lines). Because the two sets of holes are punched independently, the corners of line-perforated stamps often show irregular patterns where the horizontal and vertical lines do not meet precisely. You might see extra holes, missing holes, or slightly offset holes at the corners. Line perforation was used extensively in the 19th and early 20th centuries.

Comb Perforation

Comb perforation punches three sides of a stamp (or a row of stamps) simultaneously in a single stroke, creating a pattern that resembles a comb. The "teeth" of the comb create the two vertical sides, while the "spine" creates the horizontal separation. This method produces much cleaner, more uniform corners than line perforation because the horizontal and vertical holes are created in a single coordinated action. Comb perforation became the standard method for most postal authorities from the early 20th century onward.

Harrow Perforation

Harrow perforation is the most efficient method, punching all the perforation holes for an entire sheet (or a large section of it) in a single operation. A harrow perforating plate contains pins arranged to perforate every separation between stamps at once. This produces the most uniform results with perfectly aligned corners. Harrow perforation is most commonly associated with modern stamp production.

Rotary Perforation

Rotary perforation uses a cylindrical wheel with perforating pins that rolls across the sheet continuously, punching holes as it moves. This method is fast and efficient, making it ideal for high-volume production. Rotary perforations are common on coil stamps and many modern sheet stamps. The holes produced by rotary perforators are sometimes slightly oval or elongated compared to the round holes created by flatbed methods.

Common Perforation Sizes

While stamps have been issued with perforation measurements ranging from about 7 to 16, certain sizes are far more common than others:

Perf Size	Description	Common Usage
Perf 10	Large holes, wide spacing	Many US coil stamps, early 20th century issues
Perf 11	Medium-large spacing	Common on US stamps 1900s-1930s, many worldwide issues
Perf 12	Standard medium spacing	The most common measurement worldwide, used by many countries
Perf 13	Medium-fine spacing	Common on European stamps, Australian definitives
Perf 14	Fine spacing	Very common on British and British Commonwealth stamps
Perf 15	Very fine spacing	Some French and colonial issues

Perforation Varieties That Add Value

Perforation varieties are among the most sought-after stamp errors. Here are the main types that collectors prize:

Imperforate Stamps

Imperforate stamps are those that should have been perforated but were not. They result from sheets that bypassed the perforating machine entirely. Imperforate errors are typically very rare because quality control usually catches unperforated sheets before they reach post offices. An imperforate pair (two stamps still joined together) is more desirable than a single because it proves the stamps were never perforated, rather than simply being trimmed.

Part-Perforate Stamps

Part-perforate stamps have perforations on some sides but not others (beyond what is normal for coil or booklet stamps). These errors occur when a sheet is partially fed through the perforating machine or when the machine jams mid-operation. Common varieties include stamps perforated on only one, two, or three sides. These are rarer than fully imperforate stamps in many cases and can command significant premiums.

Double Perforations

Double perforations occur when a sheet is run through the perforating machine twice, creating two sets of holes where there should be one. The result is a stamp with a visible double row of perforation holes along one or more edges. Double perforations are relatively easier to spot than some other varieties and are popular with collectors due to their visual impact.

Shifted Perforations

When the perforation equipment is not properly aligned with the printed stamp designs, the resulting perforations are shifted to one side, creating dramatically misaligned stamps. Extreme shifts can result in stamps showing parts of adjacent designs, which are particularly collectible. Minor shifts are common and generally do not add value, but dramatic shifts that noticeably alter the stamp's appearance are sought after.

Blind Perforations

Blind perforations occur when the perforating pins press into the paper but do not fully punch through, leaving impressions or partially cut holes rather than clean perforations. This can happen when pins become worn or when the paper is too thick. Blind perfs are visible under magnification or when the stamp is held up to light.

Coil Stamps and Their Unique Perforations

Coil stamps deserve special attention because their perforations are inherently different from sheet stamps. Produced in long continuous rolls for use in vending machines and automatic affixing equipment, coil stamps are perforated on only two parallel sides:

• Horizontal coils: Perforated on the top and bottom edges only, with straight (imperforate) left and right edges
• Vertical coils: Perforated on the left and right edges only, with straight top and bottom edges

Coil stamps are often collected in pairs or strips to clearly show their coil format. A single coil stamp can sometimes be confused with a sheet stamp that has been trimmed, so pairs and strips serve as proof of the coil format. Many early US coil stamps are among the rarest and most valuable stamps in American philately, with certain varieties worth tens of thousands of dollars.

Paste-Up Pairs

When one roll of stamps ended and another began, the printer would paste the end of one roll to the beginning of the next. The resulting "paste-up pair" shows a strip of paper or tape joining two stamps from different rolls. These are collectible curiosities, particularly from early coil production.

Booklet Stamps and Straight Edges

Booklet stamps are produced in small panes that are stapled or glued into booklet covers. Stamps at the edges of booklet panes have straight (imperforate) edges where they were cut from the larger sheet. The number and position of straight edges depends on where the stamp sits in the pane:

• Corner stamps: Two straight edges (one side and either top or bottom)
• Edge stamps: One straight edge
• Interior stamps: Perforations on all four sides

Some collectors consider straight-edged stamps less desirable than fully perforated copies, while others actively seek booklet varieties. Certain booklet panes with their original covers intact are quite valuable, particularly early issues and experimental formats.

How Perforations Affect Grading and Value

Perforations are one of the most important factors in stamp grading. Here is how they impact a stamp's assessed condition:

The centering of perforations relative to the stamp design is perhaps the single most important visual factor in stamp grading. Stamps are graded on a scale from "Superb" (perfectly centered with equal margins) down through "Extremely Fine," "Very Fine," "Fine," and "Good" to "Poor." A well-centered stamp can be worth 5 to 50 times more than the same stamp with poor centering, depending on the issue.

Detecting Reperforated Stamps (Fakes)

Reperforation is the process of adding new perforations to a stamp to improve its appearance or simulate a scarcer variety. This is one of the most common forms of stamp fraud, and every collector should know how to detect it.

Signs of Reperforation

• Uneven hole size: Reperforated holes may differ slightly in size from original perforations
• Inconsistent spacing: Machine-made original perforations are very regular; hand-reperforated stamps often show slight irregularities
• Paper fibers: Original perforations push paper fibers outward; reperforated holes may show different fiber patterns
• Stamp dimensions: A reperforated stamp may be slightly smaller than normal because paper was trimmed before reperforating
• Design position: If the design seems unusually well-centered compared to other copies of the same stamp, reperforation may be suspected

For valuable stamps, professional expertizing services (such as the Philatelic Foundation or the American Philatelic Expertizing Service) can examine stamps under high magnification and with specialized equipment to detect reperforation. Getting an expert certificate is strongly recommended before purchasing expensive stamps where perforation variety is the primary value factor.

Measuring Perforations with Technology

While the traditional perforation gauge remains the standard tool, modern technology offers additional options for measuring and analyzing perforations:

• Digital perforation gauges: Electronic devices that provide precise measurements to a tenth of a perforation
• High-resolution scanning: Scanning stamps at 1200+ DPI allows you to measure perforations precisely on screen using software tools
• Smartphone apps: The StampScan app uses AI to identify stamps from photos, helping narrow down possible perforation varieties based on the identified issue

Combining traditional measurement with modern identification technology gives you the best results. Use a physical perforation gauge for precise measurement, then cross-reference with a digital catalog or stamp identification app to understand which varieties exist for the stamp you are examining.

Building a Perforation Variety Collection

Many collectors specialize in perforation varieties, and it can be a deeply rewarding area of philately. Here are some tips for getting started:

1. Start with well-documented issues: US stamps from 1908-1922 (the Washington-Franklin series) offer dozens of perforation varieties at relatively accessible prices
2. Invest in a quality gauge: Accurate measurement is everything in perforation collecting
3. Study your catalog carefully: Learn which perforation varieties exist for the stamps you are examining before you start measuring
4. Examine watermarks too: Perforation varieties often correspond with specific watermark types, and you need both to correctly identify a stamp
5. Buy from reputable dealers: For expensive perforation varieties, purchase only stamps with expert certificates

Perforation study connects you to the physical history of stamp production. Every variety represents a specific machine, a specific printer, and a specific moment in postal history. Understanding perforations deepens your appreciation of the stamps in your collection and helps ensure accurate identification and valuation.