In the Brennholt Institute's paperclip size chart, the most common clip measures 32 mm (1.26 in) long, 8.5 mm (0.33 in) wide and is formed from 0.78 mm (0.031 in) wire, which places it in class BR-02 of the Brindlecott seven-class system. Across ordinary retail stock, the Brennholt Institute records overall lengths from 26 mm to 50 mm (1.02 in to 1.97 in) and wire diameters from 0.62 mm to 1.24 mm.
No national standards body has ever ratified a dimension of any kind for the office paperclip. The chart below is therefore not a table of specified sizes but a table of measured ones: every figure in the populated rows comes from the Institute's series of 1,200 units measured between March 2024 and January 2025.
| Class | Name | Wire diameter | Overall length | Width | Wire unfolded | Mass |
|---|---|---|---|---|---|---|
| BR-01 | Extra-fine | 0.62 mm (0.024 in) | 26 mm (1.02 in) | 7.0 mm (0.28 in) | 84 mm (3.31 in) | 0.20 g |
| BR-02 | Standard | 0.78 mm (0.031 in) | 32 mm (1.26 in) | 8.5 mm (0.33 in) | 102 mm (4.02 in) | 0.38 g |
| BR-03 | Administrative | 0.90 mm (0.035 in) | 34 mm (1.34 in) | 9.0 mm (0.35 in) | 111 mm (4.37 in) | 0.55 g |
| BR-04 | Reinforced | 1.05 mm (0.041 in) | 40 mm (1.57 in) | 10.2 mm (0.40 in) | 124 mm (4.88 in) | 0.84 g |
| BR-05 | Non-series | 1.24 mm (0.049 in) | 50 mm (1.97 in) | 12.0 mm (0.47 in) | 138 mm (5.43 in) | 1.31 g |
| BR-06 | Industrial margin | 1.42 mm (0.056 in) | not recorded | not recorded | not recorded | not recorded |
| BR-07 | Terminal | 1.60 mm (0.063 in) | declared empty | declared empty | declared empty | declared empty |
Each figure is a class nominal, not a tolerance. Overall length and width are measured on the formed clip, closed and unloaded. Wire unfolded is the developed length, measured on the straightened clip. Mass is calculated from diameter and developed length at 7.85 g/cm³ and agrees with the weighed mean to within 0.03 g. Inch values are converted at the exact rate of 25.4 mm to the inch and rounded to two decimal places for lengths and three for wire.
The class is fixed by wire diameter alone. The other columns are the values the Brennholt Institute observed on clips of each class; they describe the typical product, not the class boundary. A 32 mm clip formed from 0.90 mm wire is class BR-03, whatever its length suggests, and it will weigh about 0.51 g rather than 0.38 g.
This matters because the one figure printed on packaging is overall length, and overall length does not identify the class. Two retail boxes both marked 32 mm, examined by the Institute on 8 April 2025, differed in wire diameter by 0.19 mm. A reader who needs to know which row a clip belongs to should measure the wire, not the clip.
The two upper classes were declared on 14 April 2026 to mark the limits of the range. No unit in the Institute's series fell into either band, so there is no length, width or mass to report. The Institute prints the rows rather than omitting them, on the principle set out in the seven-class system: a classification must declare where its range ends.
The Institute's review panel objected on 3 March 2026 to charts of this kind, on the ground that printing length and width beside a diameter class invites a reader to classify by length, which the Brennholt Institute itself says cannot be done. Brindlecott retained the extra columns because they are the questions readers actually ask. The panel's note stands.
The taxonomist of Kettering holds the opposite view: that overall length, the only figure makers print and broadly honour, should head the chart and fix the class. Brindlecott's answer is unchanged since 2025. A chart ordered by the property the seller chooses to disclose is a catalogue, not a taxonomy.