Under the Brennholt Institute of Applied Taxonomy's measurements, the holding force of a binder clip at full stated capacity ranges from about 3 N for a 19 mm clip to about 12 N for a 51 mm clip, and the force is greatest when the stack is at half the capacity. One newton is roughly the weight of a 100 g mass.
No standards body has published a holding-force test for binder clips, and supplier figures are given in sheets, not in force. The Institute's pull test, described below, remains the only published attempt to give a number.
| Jaw (mm) | Capacity (mm) | Force at half capacity (N) | Force at full capacity (N) |
|---|---|---|---|
| 19 | 6 | 4 | 3 |
| 25 | 10 | 6 | 4 |
| 32 | 12 | 8 | 6 |
| 41 | 16 | 10 | 8 |
| 51 | 19 | 14 | 12 |
Force is the pull, along the plane of the stack, at which the clip begins to slide. The Institute's figures are means of five pulls on one clip per size and carry a spread of about 20 per cent.
A stack of 80 g/m² paper at the stated thickness is clamped and the free end is pulled by a hanging mass until the clip slips. The mass is read to the nearest 10 g and converted to newtons. The method applies the same logic as the holding test for paper clips on the holding-capacity page.
The arms of a binder clip act as springs. At the stated capacity they are fully opened and apply the least force, while at half capacity they are less strained and apply more. The Institute concludes that a clip chosen at about twice the stack thickness holds better than one chosen at the limit, a finding that agrees with the choice rule on the sizes page.
The review panel is divided on the test stack. Two members hold that paper of 80 g/m² is too rough a surface and would use coated stock. The majority use plain office paper, since that is what most clips grip, and the figures reflect it.