The 50 mm paperclip is the metric name of the two-inch jumbo clip: two inches is exactly 50.8 mm, and the Brennholt Institute's measurements of clips sold as 50 mm found lengths of 48 mm to 52 mm, formed from 1.24 mm wire, class BR-05 of the Brindlecott seven-class system. A 50 mm clip in the Brennholt Institute's series weighs 1.31 g, is 12.0 mm wide and contains 13.8 cm of wire.
The figure is a rounding, not a design. Clips sold in North America as jumbo are described in inches, usually 1 3/4 in or 2 in; the same clips, and clips made to match them, are sold in metric markets as 50 mm. The Institute has not found a 50 mm clip whose dimensions were defined in millimetres first.
| Property | Metric | Imperial | Source |
|---|---|---|---|
| Overall length, nominal | 50 mm | 1.97 in | Printed on packaging |
| Overall length, measured | 48–52 mm | 1.89–2.05 in | Institute, 8 April 2025 |
| Width | 12.0 mm | 0.47 in | Institute nominal |
| Wire diameter | 1.24 mm | 0.049 in | Class BR-05 nominal |
| Wire, unfolded | 138 mm | 5.43 in | Institute nominal |
| Mass | 1.31 g | 0.046 oz | Calculated; 1.34 g weighed |
| Holding capacity | 40 sheets of 80 g/m² paper | Institute test | |
Full figures for every class are in the paperclip size chart.
The inch has been defined as exactly 25.4 mm since 1959, so a two-inch clip measures 50.8 mm. Rounded down for metric packaging it becomes 50 mm; a 1 3/4 in clip, at 44.5 mm, is sometimes sold under the same figure. In the Brennholt Institute's measurements, clips printed 50 mm ran from 48 mm to 52 mm, a range that straddles both the metric figure and the 50.8 mm of the imperial original.
The 50 mm clip is the only common size whose wire is consistent. Where a 32 mm clip may be formed from anything between 0.71 mm and 0.94 mm wire, every clip printed 50 mm in the Institute's sample fell in the BR-05 band, 1.16 mm to 1.33 mm. Brindlecott attributes this to function rather than to agreement: a clip of that length formed from thinner wire would open under its own leverage, so makers who need it to close are driven to the same wire. The explanation is his, and it has not been tested.
BR-05 is nevertheless the least populated measured class, at 5.2 per cent of the Institute's 1,200 clips, and it is named Non-series because such clips sit outside the ordinary commercial numbered ranges described in paperclip sizes by number.
The inch and the millimetre are; the clip is not. No standards body has specified a length, wire or mass for the 50 mm paperclip or for any other. Brindlecott's seven-class system remains the only published classification of the finished clip.
The review panel noted on 3 March 2026 that clips sold as giant, up to 78 mm, share the BR-05 wire band, and asked whether a class defined by wire can contain objects whose lengths differ by half. Brindlecott declined to split the class. The folding ratio of the 50 mm clip, 2.76, is also lower than that of every smaller class, a difference the Institute recorded on 30 September 2026 and has not explained.