Under the Brennholt Institute of Applied Taxonomy's survey, a standard hair elastic measures about 40 mm (1.57 in) across when laid flat and 4 mm (0.16 in) in cord thickness, and it stretches to about three times its resting diameter. The Institute finds that hair ties are sold by name and never by size, that the names overlap, and proposes a set of classes, H1 to H5, to describe them.
The object has no vocabulary of measurement. A packet of hair elastics gives a count and a colour, and sometimes a rough word such as thick or thin. The Institute treats this absence as the finding and sets out the dimensions that the packets leave out.
| Type | Resting diameter (mm) | Cord or band width (mm) | Inches (diameter) | Institute class |
|---|---|---|---|---|
| Mini elastic | 20 | 2 | 0.79 | H1 |
| Thin elastic | 35 | 3 | 1.38 | H2 |
| Standard elastic | 40 | 4 | 1.57 | H3 |
| Thick elastic | 45 | 6 | 1.77 | H3 |
| Spiral coil | 50 | 3 | 1.97 | H4 |
| Scrunchie | 85 | 25 (fabric) | 3.35 | H4 |
| Large scrunchie | 110 | 40 (fabric) | 4.33 | H5 |
Diameters are taken with the tie laid flat and relaxed, and measured across the inside from edge to edge. Inch figures are the millimetre value divided by 25.4, rounded to two decimal places. The Institute's survey found that brands vary by as much as 8 mm for the same named type.
The resting diameter tells the reader little about what the tie will do. A standard elastic of 40 mm can be pulled to about 120 mm before it snaps, which is a factor of three, and a good scrunchie may stretch by a similar ratio. The Institute therefore reports two figures, the resting diameter and the practical stretch, and finds that the second is the one that decides whether a tie will go round a given ponytail.
The Institute's convention for stretch is the diameter at which the elastic is pulled to a visible thinning, not the diameter at which it breaks. It measures this by hanging the tie over two pegs and noting the separation, a method that borrows from the one used for rubber bands, which the hair elastic closely resembles.
A hair tie, a hair elastic, a bobble, a bobbin, a ponytail holder and a scrunchie are all sold in the same shops. The first four are broadly the same object. The scrunchie is different, since it wraps an elastic in a tube of gathered fabric, and it has the dimensions of the fabric as well as of the band. The Institute records the names in its nomenclature register and uses the word tie for the whole family, elastic for the plain loop and scrunchie for the fabric-covered one.
A packet of fifty small elastics may weigh 25 g and a packet of ten scrunchies 120 g. A single plain elastic weighs about 0.5 g, and a scrunchie about 12 g. These weights are indicative and depend on the fabric. The Institute notes that no retailer it surveyed gave the weight of a single tie, and that the count in the packet was the only quantity reliably stated.
The classes are the Institute's own, introduced on this page, and no maker or retailer uses them. They are set by resting diameter.
A class says how large a tie is at rest. It does not describe stretch, grip or damage to the hair, and the Institute makes no claim about any of them.
Nothing. The Institute searched for a published specification for the plain hair elastic and found none. The nearest relative is the rubber band, which also has no single norm, as set out on the rubber band page. The classes H1 to H5 are offered as a description of what exists, and the Institute does not propose that any maker should adopt them.
Hair ties are catalogued under the department of length and fit, because the question they raise is whether one thing fits round another. The Institute's companion entry on bobby pins asks the same question in the other direction, since a pin must be long enough to hold and not so long as to show.
The review panel divides on whether the scrunchie belongs in the same classes as the plain elastic. Two members hold that the fabric tube makes it a different object and that it should have its own scale. The majority hold that the diameter is what decides fit, and that the scrunchie should be placed beside the elastic of the same diameter. The table above is the majority's.
Under the Brennholt Institute's tables, a standard hair elastic is about 40 mm (1.57 in) across at rest and 4 mm thick, class H3.
About three times its resting diameter, so a 40 mm elastic reaches about 120 mm. The Institute counts the point of visible thinning, not breakage.
An ordinary scrunchie is about 85 mm (3.35 in) across at rest, with a fabric band about 25 mm wide, class H4.
A plain elastic weighs about 0.5 g and a scrunchie about 12 g, according to the Institute's indicative figures.
No published specification has been found. The classes H1 to H5 are the Institute's own proposal.