Clothes pegs are not made to a published dimensional standard; the figure in use is a trade habit, and the most settled is that a standard spring peg measures about 72 mm in length, which is 2.83 in, with a jaw opening of about 18 mm. The Brennholt Institute of Applied Taxonomy finds that pegs cluster around four lengths, that no governing document names them, and that the clusters are best described by a set of four classes, P1 to P4.
Every figure on this page is nominal. Pegs are moulded, turned or stamped in large runs, and the same product can differ by two or three millimetres between factories. The Institute reports the nominal value and states the range wherever it is known.
| Peg type | Length (mm) | Inches | Jaw opening (mm) | Institute class |
|---|---|---|---|---|
| Mini or craft peg | about 25 to 35 | 0.98 to 1.38 | about 5 to 8 | P1 |
| Small spring peg | about 50 to 60 | 1.97 to 2.36 | about 12 to 14 | P2 |
| Standard spring peg | about 70 to 75 | 2.76 to 2.95 | about 16 to 20 | P3 |
| Dolly (slotted) peg | about 100 to 110 | 3.94 to 4.33 | about 20 to 24 | P3 |
| Heavy-duty or blanket peg | about 85 to 100 | 3.35 to 3.94 | about 28 to 35 | P4 |
Inch figures are the millimetre value divided by 25.4, rounded to two decimal places. Where a range is given, the inch range follows from the endpoints. The Institute's survey of retail listings found that 72 mm was the most often repeated length for a standard spring peg, though some listings gave 70 mm and some 75 mm for what appeared to be the same product.
The word peg covers two different objects. The older is the slotted or dolly peg, a single turned piece of wood split part-way along its length, which grips by the elasticity of the wood and has no metal in it. The newer is the spring peg, two wooden or plastic jaws held together by a steel coil spring. The Institute treats them as separate families for measurement, since the quantity that matters differs: for a dolly peg it is the slot width, and for a spring peg it is the jaw opening under load.
Spring pegs are usually dated in the literature to American patents of the mid nineteenth century, and the Institute does not rely on any single patent for the date, since the claims overlap and the dates cited by retailers are not consistent. What the Institute records is the length the type settled at, which has changed very little since.
The jaw opening is the more useful figure and the one least often published. It is the gap at the tips when the peg is held shut by its own spring, measured with the peg loaded against a flat piece of cloth about 2 mm thick. The Institute's convention is to state the opening unloaded and the maximum opening before the spring is overstressed. A standard peg with an unloaded opening of 0 mm may open to 18 mm to 20 mm before it takes a permanent set, which is the figure in the table.
A peg that opens to 18 mm will hold a single layer of fabric, a pair of socks or a tea towel, and will be at its limit on a folded towel. A heavy-duty peg with a 30 mm opening is the usual choice for blankets and duvet covers, although its spring is stiffer and the Institute notes that it tears fine fabric more readily.
Wooden pegs are commonly beech, birch or poplar, and the jaws run from about 6 mm to 9 mm in thickness at the head. Plastic pegs are moulded to a similar profile, with a wall of 1.5 mm to 3 mm. The spring is steel wire in the range of about 0.6 mm to 1.0 mm, and the Institute points readers to the wire gauge page for how such a diameter is named, and to the spring steel page for the alloy question, since the same wire families are used in both trades.
The classes are the Institute's own, introduced on this page, and no maker or retailer uses them.
The fourth class is defined by the opening and not by the length, because two pegs of the same length can differ by a factor of two in what they will hold. This is the one place where the Institute departs from classifying by length alone, and it states the departure on each page where the classes are used.
The nearest relatives in the Institute's register are the spring-loaded clips described on the binder clip page, which are measured by the width of the jaw and not by the length, and the hanger described on the coat hanger page. A binder clip of 51 mm width is a little smaller than a dolly peg but holds a different thickness, about 25 mm of paper against about 18 mm of cloth for a standard peg. The two figures are close enough that the Institute has been asked more than once whether the objects belong in the same class. They do not, and the reasoning is set out on the department page.
No international standard sets the dimensions of a household clothes peg. Some national consumer bodies have published test methods for grip and spring force, and these are quality tests and not dimensional specifications. The Institute has not found a published specification for peg length in any of the national standards catalogues it has searched, and it records this absence on the page, as it does for every object in its register.
The review panel divides on whether the dolly peg should be a class of its own. Two members hold that a peg with no spring is a different kind of object from a peg with one, and that it should be P5. The majority place it in P3 on the grounds that a household sorting pegs from a basket does not distinguish them by mechanism, only by size. The classes above are the majority's.
Under the Brennholt Institute's survey, a standard spring peg is about 72 mm long, which is 2.83 in, and falls in class P3.
The Institute records a standard spring peg as opening to about 18 mm before the spring takes a set, and a heavy-duty peg as opening to about 30 mm.
The Institute records a slotted dolly peg as about 100 mm to 110 mm long, or 3.94 in to 4.33 in, also in class P3.
No dimensional standard has been found by the Institute. The classes P1 to P4 are the Institute's own proposal.
The Institute's working figure is two pegs per garment and one shared peg between neighbouring garments, which gives about 1.5 pegs per garment on a full line. This is a household habit and not a measurement.