Perforations explained: how to measure them

Perforations are the rows of small holes that let stamps be separated from a sheet. To a collector they are also a vital clue: the same design is sometimes printed with different perforations, and catalogues list these as separate varieties — with very different values.

What "perf 14" means

Perforations are measured as the number of holes in a length of 2 centimetres. A stamp described as perf 14 has 14 perforation holes in every 2 cm along its edge. This standard has been used by catalogues since the 1860s.

Using a perforation gauge

A perforation gauge is a card or plastic ruler printed with rows of dots or lines at different spacings.

1. Place the stamp on the gauge with one edge lying along a row.
2. Slide it down the scale until the teeth of the stamp match the dots exactly, with every tooth aligned along the whole edge.
3. Read the number beside that row.

Measure both the top and a side edge. Many stamps have different perforations horizontally and vertically.

Compound perforations

When the two directions differ, catalogues write them as, for example, perf 13½ × 14. By convention the horizontal measurement (top and bottom) comes first and the vertical (sides) second.

Other separations

• Imperforate stamps have no perforations at all and had to be cut apart with scissors. Look for even, generous margins on all four sides.
• Rouletting uses small cuts or slits instead of holes, so no paper is removed.
• Die-cut edges are used on most modern self-adhesive stamps; they may imitate the wavy look of perforations.

Tips

• Measure on a flat surface in good light; a magnifier helps.
• Do not measure a stamp whose edges have been trimmed — the result will be wrong.
• Record the perforation in your album write-up; it shows careful study, which exhibition judges notice.