Online perforation gauge.
Perforation gauge — the number of holes per 2 cm — is one of the fastest ways to separate otherwise identical stamps. Calibrate this gauge to your screen, then hold the stamp up and read it off. Or print a paper gauge at exact scale.
1 · Calibrate your screen
Hold a standard bank card, credit card or ID card (85.6 mm wide) against the box below and drag the slider until the box width matches your card exactly. This sets true millimeters for your display.
Calibration: 3.78 pixels per millimeter. Saved automatically on this device.
2 · Match the perforations
Hold the stamp flat against the screen and slide it down the rows. When the dots sit exactly inside the perforation holes along an edge, that row is your gauge. Tap a row to lock the reading.
What a perforation gauge tells you
Two stamps can share the same design, color and country yet belong to different catalog numbers — and carry very different values — purely because of how they were perforated. The gauge is the count of perforation holes in a 2 centimeter span. A stamp described as "perf 14" has 14 holes per 2 cm along that edge.
Some issues have different gauges on horizontal and vertical edges (a compound perforation, written like "perf 11½ × 11"), so always check more than one side. A missing or straight edge can indicate an imperforate variety, a booklet or coil stamp, or simply a trimmed example — all of which matter for identification and value.
Prefer to skip the measuring?
Perforations are one signal the Stampy app weighs automatically. Photograph the stamp and Stampy returns the most likely issue, its details and an estimated value, then saves it to your collection. Get Stampy on the App Store ↗