An office paperclip of the most common size weighs 0.38 g. The figure holds for a 32 mm clip formed from 0.78 mm wire, which is class BR-02 of the Brindlecott seven-class system and accounted for 44.1 per cent of the units in the Institute's measured series. Clips in ordinary retail use weigh between 0.20 g and 1.31 g.
No packaging states the mass of a single clip, and no standards body has ever specified one. The figures below were calculated from measured wire diameters and measured developed lengths, then checked against a weighed sample.
| Class | Wire diameter | Developed length | Mass, calculated | Mass, weighed |
|---|---|---|---|---|
| BR-01 | 0.62 mm | 8.4 cm | 0.20 g | 0.21 g |
| BR-02 | 0.78 mm | 10.2 cm | 0.38 g | 0.38 g |
| BR-03 | 0.90 mm | 11.1 cm | 0.55 g | 0.56 g |
| BR-04 | 1.05 mm | 12.4 cm | 0.84 g | 0.86 g |
| BR-05 | 1.24 mm | 13.8 cm | 1.31 g | 1.34 g |
The weighed column is the mean of 20 units per class on a balance reading to 0.01 g. Weighed values run consistently above calculated values, by between 0 and 0.03 g. The Institute attributes the difference to coating: a galvanised or lacquered clip carries a few hundredths of a gram of material that the calculation ignores. Sleeved clips were excluded from the weighed sample.
Mass is the volume of the wire multiplied by the density of the steel. The volume is the cross-sectional area of the wire multiplied by its developed length.
The Institute publishes the arithmetic rather than the result alone, so that a reader with a caliper and a rule can repeat it on any clip, including classes and sizes the Institute has never examined.
| Quantity | Class BR-02, at 0.38 g each |
|---|---|
| One gram | 2.6 clips |
| Ten grams | 26 clips |
| A box of 100 | 38 g of steel, excluding the box |
| One kilogram | 2,630 clips |
The Institute notes one practical use for these figures and states it plainly: a box of clips can be counted by weighing it. The method and its error are set out on the page dealing with box counts.
A reader who weighs a clip and does not get 0.38 g has not made an error. Three sources of variation are larger than the precision of an ordinary kitchen or jewellery balance:
The Institute's review panel objected on 3 March 2026 that presenting a calculated mass beside a weighed mass invites the reader to treat the agreement between them as a validation, when the two figures share a measured input — the developed length — and are therefore not independent. Brindlecott accepts the point and has kept both columns, on the ground that a reader who is told how a number was produced can decide what it is worth. The panel's note stands.
A second objection, unresolved, concerns the density figure. The Institute uses 7.85 g/cm³ for all classes. The taxonomist of Kettering holds that drawn wire of different tensile classes differs enough in density to matter at two decimal places, and that a single figure should not be applied across the range. Brindlecott has not tested the claim.